bluuebunny/crossref_metadata_2025_split huggingface dataset:
The low‐energy electronic properties of graphene ribbons in spatially modulated magnetic fields
Authors: Wu J. Y. , Lin M. F. 
Published: September 2008

AbstractThe low energy magnetoelectronic structures for a nanographene ribbon under modulated magnetic fields are investigated through the Peierls tight‐binding model. They are dominated by the field strength, period, phase, the ribbon width, and edge structure. The modulated magnetic field could add state degeneracy, modify energy dispersions, alter subband spacings, affect carrier‐density distributions, create additional band‐edge states, and extend the partial flat bands. The main features of energy bands are directly reflected in density of states, such as the position, the height, the structure, and the number of the prominent peaks. These results are compared with a zigzag ribbon under a uniform magnetic field. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Exciton transfer and propagation in carbon nanotubes studied by near‐field optical microscopy
Authors: Qian Huihong , Georgi Carsten , Anderson Neil , Green Alexander A. , Hersam Mark C. , Novotny Lukas , Hartschuh Achim 
Published: September 2008

AbstractWe studied transfer and propagation of excitons in single semiconducting carbon nanotubes using high resolution tip‐enhanced near‐field photoluminescence microscopy. Exciton energy transfer is found to occur from a larger band gap nanotube to a smaller band gap nanotube. Efficient transfer however is found to be limited to a few nanometers because of competing fast non‐radiative relaxation and can be explained in terms of electromagnetic near‐field coupling. Towards the end of a nanotube, photoluminescence decay is observed on a length scale of 50–90 nm which is attributed to exciton propagation followed by additional non‐radiative relaxation at the nanotube end. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Capillary filling of single‐walled carbon nanotubes with ferrocene in an organic solvent
Authors: Shiozawa Hidetsugu , Giusca Cristina E. , Silva S. Ravi P. , Kataura Hiromichi , Pichler Thomas 
Published: September 2008

AbstractCapillary reactions of single‐walled carbon nanotubes have been investigated both in ferrocene‐saturated acetone and in ferrocene vapor. The encapsulations of ferrocene are observed as subsequent growth of inner shell tubes. From Raman spectroscopy we show that the filling yield is about ten times higher with the vapor filling. The inner tube – outer tube pair distributions are identical for both converted samples and different to the one grown from the fullerene precursor. The largest assigned inner shell tube from ferrocene is (11,0), which is not available from the fullerene precursor. This result is attributed to the catalytic growth mechanism enabling a wide diameter range of inner shell tubes. The solvent based filling provides for a quick analysis of possible molecule guest – nanotube host pairs with a moderate filling factor. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Combined STM/STS, TEM/EELS investigation of CNx‐SWNTs
Authors: Lin H. , Lagoute J. , Chacon C. , Arenal R. , Stéphan O. , Repain V. , Girard Y. , Enouz S. , Bresson L. , Rousset S. , Loiseau A. 
Published: September 2008

AbstractNitrogen doped single‐walled carbon nanotubes (CNx ‐SWNTs) were successfully synthesized by vaporizing a C:Ni/Y target by a CO2 continuous laser under a nitrogen atmosphere. The as‐grown nanotubes were investigated by combining TEM/EELS and STM/STS techniques. According to TEM observations, the tubes are mostly single‐walled and few defects are found. Local chemical characterization was performed by EELS analysis, which proves the presence of nitrogen in both individual tubes and SWNTs bundles and indicates a nitrogen concentration around 1 at.%. STM observations of CNx ‐SWNTs have been then undertaken and atomic resolution images were obtained. First STM analyses of these nanotubes show some defects which have never been observed in pure carbon nanotubes before. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
ODMR of NV centers in nano‐diamonds covered with N@C60
Authors: Huebener Kati , Schoenfeld Rolf Simon , Kniepert Juliane , Oelmueller Christoph , Harneit Wolfgang 
Published: September 2008

AbstractWe report on experiments to detect electron spins in the molecular system N@C60 indirectly by coupling them to electron spins in diamond. The spin of single or multiple nitrogen‐vacancy (NV) centers in nano‐diamonds can be routinely measured using optically detected magnetic resonance (ODMR) in a confocal microscopy setup. Line splittings similar to those expected for coupling to external spins are sometimes seen in the ODMR spectra. Direct comparison of spectra on individual nano‐diamonds before and after coverage with fullerenes however gave no clear evidence that the spin‐spin coupling was due to N@C60. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Surface enhanced Raman spectroscopy of the liquid crystal 8CB using chip structures
Authors: Plank W. , Hulman M. , Kuzmany H. , Köck A. , Roppert K. , Kukovecz A. , Krenn J. , Bischof R. 
Published: September 2008

AbstractMolecular nanostructures are excellent systems to study surface enhanced Raman scattering (SERS), since monolayers or sub‐monolayers are expected to provide maximum scattering enhancement. The SERS enhancement is due to a plasma induced field enhancement by metallic nanoparticles. By this effect the Raman response of molecules in the immediate neighborhood of the particles can be dramatically increased. We investigated the SERS effect of Ag colloids on glass substrates and on lithographically produced nanostructures of gold and aluminum on silicon and ITO‐glass.For testing extremely thin layers (monolayers and submonolayers) of 4‐octyl‐4′‐cyanobiphenyl (liquid crystal 8CB) were prepared. The observed enhancement for 8CB on Ag colloids was about 103. Enhancement factors for the lithographic structures were initially below 100. To increase the enhancement the Au nanostructures were coated with a 20 nm thick Ag‐layer. Optimisation of the Ag nanoparticle geometry was investigated as an alternative SERS improvement routine. The viability of the chip structures for multiple usage was tested. The experimental analysis was supported by calculations of the SERS cross‐section for different structure geometries. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Carbon nanotubes – A scientometric study
Authors: Marx Werner , Barth Andreas 
Published: September 2008

AbstractThis study has been carried out to analyze the carbon nanotubes research field by scientometric methods. The data are based on the Thomson/ISI Web of Science (WoS) and on the literature file of the Chemical Abstracts Service (CAS). The time dependent overall number of articles dealing with nanotubes is given. The data reveal a dramatic increase of basic research activity in this research field. The most productive authors and leading research organizations are determined. The distribution of the nanotubes articles on the countries of the authors and on the leading journals is given. The citation data of nanotubes articles are discussed: The average citation rate of nanotubes related articles and of articles out of other currently popular research fields published in the year 2000 are compared with the average citation rates in chemistry and physics. The time evolution of the most highly cited nanotubes papers and of the complete ensemble of the nanotubes articles published in 2000 are shown. The impact of two nanotubes papers appeared prior to 1991 is discussed. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Uncertainties in the oxygen isotopic composition of barium sulfate induced by coprecipitation of nitrate
Authors: Michalski Greg , Kasem Michelle , Rech Jason A. , Adieu Sabine , Showers William S. , Genna Bernie , Thiemens Mark 
Published: September 2008

AbstractCoprecipitation of nitrate and sulfate by barium has probably resulted in significant error in numerous studies dealing with the oxygen isotopic composition of natural sulfates using chemical/thermal conversion of BaSO4 and analysis by isotope ratio mass spectrometry. In solutions where NO/SO molar ratios are above 2 the amount of nitrate coprecipitated with BaSO4 reaches a maximum of approximately 7% and decreases roughly linearly as the molar ratio decreases. The fraction of coprecipitated nitrate appears to increase with decreasing pH and is also affected by the nature of the cations in the precipitating solution. The size of the oxygen isotope artifact in sulfate depends both on the amount of coprecipitated nitrate and the δ18O and Δ17O values of the nitrate, both of which can be highly variable. The oxygen isotopic composition of sulfate extracted from atmospheric aerosols or rain waters are probably severely biased because photochemical nitrate is usually also present and it is highly enriched in 18O (δ18O ∼50–90‰) and has a large mass‐independent isotopic composition (Δ17O ∼20–32‰). The sulfate δ18O error can be 2–5‰ with Δ17O artifacts reaching as high as 4.0‰. Copyright © 2008 John Wiley & Sons, Ltd.
Negative ion electrospray ionization mass spectrometry of nucleoside phosphoramidate monoesters: elucidation of novel rearrangement mechanisms by multistage mass spectrometry incorporating in‐source deuterium labelling
Authors: Xu Peng‐Xiang , Hu An‐Fu , Hu Dan , Gao Xiang , Zhao Yu‐Fen 
Published: September 2008

AbstractSeveral O‐2′,3′‐isopropylideneuridine‐O‐5′‐phosphoramidate monoesters were synthesized and analyzed by negative ion electrospray ionization tandem mass spectrometry (ESI‐MSn). Two kinds of novel rearrangement reactions were observed due to the difference in the amino acid in the nucleoside phosphoramidate monoesters, and possible mechanisms were proposed. One involves a five‐membered cyclic transition state. The other is formation of a stable five‐membered ring intermediate by Michael addition. Results were confirmed by tandem mass spectrometry and isotopically labeled hydrogen atoms. Furthermore, the internal hydrogen exchange between active hydrogen and methyl acrylate in the heated capillary of the mass spectrometer was found. The characteristic fragmentation behavior in ESI‐MS may be used to monitor this kind of compounds in the biological metabolism. Copyright © 2008 John Wiley & Sons, Ltd.
Real‐time, on‐line monitoring of organic chemical reactions using extractive electrospray ionization tandem mass spectrometry
Authors: Zhu Liang , Gamez Gerardo , Chen Huan Wen , Huang Hao Xi , Chingin Konstantin , Zenobi Renato 
Published: September 2008

AbstractExtractive electrospray ionization mass spectrometry (EESI‐MS) for real‐time monitoring of organic chemical reactions was demonstrated for a well‐established pharmaceutical process reaction and a widely used acetylation reaction in the presence of a nucleophilic catalyst, 4‐dimethylaminopyridine (4‐DMAP). EESI‐MS provides real‐time information that allows us to determine the optimum time for terminating the reaction based on the relative intensities of the precursors and products. In addition, tandem mass spectrometric (MS/MS) analysis via EESI‐MS permits on‐line validation of proposed reaction intermediates. The simplicity and rapid response of EESI‐MS make it a valuable technique for on‐line characterization and full control of chemical and pharmaceutical reactions, resulting in maximized product yield and minimized environmental costs. Copyright © 2008 John Wiley & Sons, Ltd.
FiD: a software for ab initio structural identification of product ions from tandem mass spectrometric data
Authors: Heinonen Markus , Rantanen Ari , Mielikäinen Taneli , Kokkonen Juha , Kiuru Jari , Ketola Raimo A. , Rousu Juho 
Published: September 2008

AbstractWe present FiD (Fragment iDentificator), a software tool for the structural identification of product ions produced with tandem mass spectrometric measurement of low molecular weight organic compounds. Tandem mass spectrometry (MS/MS) has proven to be an indispensable tool in modern, cell‐wide metabolomics and fluxomics studies. In such studies, the structural information of the MSn product ions is usually needed in the downstream analysis of the measurement data. The manual identification of the structures of MSn product ions is, however, a nontrivial task requiring expertise, and calls for computer assistance. Commercial software tools, such as Mass Frontier and ACD/MS Fragmenter, rely on fragmentation rule databases for the identification of MSn product ions. FiD, on the other hand, conducts a combinatorial search over all possible fragmentation paths and outputs a ranked list of alternative structures. This gives the user an advantage in situations where the MS/MS data of compounds with less well‐known fragmentation mechanisms are processed. FiD software implements two fragmentation models, the single‐step model that ignores intermediate fragmentation states and the multi‐step model, which allows for complex fragmentation pathways. The software works for MS/MS data produced both in positive‐ and negative‐ion modes. The software has an easy‐to‐use graphical interface with built‐in visualization capabilities for structures of product ions and fragmentation pathways. In our experiments involving amino acids and sugar‐phosphates, often found, e.g., in the central carbon metabolism of yeasts, FiD software correctly predicted the structures of product ions on average in 85% of the cases. The FiD software is free for academic use and is available for download from www.cs.helsinki.fi/group/sysfys/software/fragid. Copyright © 2008 John Wiley & Sons, Ltd.
Counting without sampling: Asymptotics of the log‐partition function for certain statistical physics models
Authors: Bandyopadhyay Antar , Gamarnik David 
Published: September 2008

AbstractIn this article we propose new methods for computing the asymptotic value for the logarithm of the partition function (free energy) for certain statistical physics models on certain type of finite graphs, as the size of the underlying graph goes to infinity. The two models considered are thehard‐core(independent set) model when theactivityparameter λis small, and also the Potts (q‐coloring) model. We only consider the graphs withlarge girth. In particular, we prove that asymptotically the logarithm of the number ofindependent setsof anyr‐regular graph with large girth when rescaled is approximately constant ifr≤ 5. For example, we show that every 4‐regularn‐node graph with large girth has approximately (1.494…)n‐many independent sets, for largen. Further, we prove that for everyr‐regular graph withr≥ 2, withnnodes and large girth, the number of properq≥r+ 1 colorings is approximately${[q{(1 - {1 \over q})}^{r \over 2} ]^n}$n, for largen. We also show that these results hold for random regular graphs with high probability (w.h.p.) as well.As a byproduct of our method we obtain simple algorithms for the problem of computing approximately the logarithm of the number of independent sets and proper colorings, in low degree graphs with large girth. These algorithms are deterministic and use certain correlation decay properties for the corresponding Gibbs measures, and its implications to uniqueness of the Gibbs measures on the infinite trees, as well as some simplecavity trickwhich is well known in the physics and the Markov chain sampling literature.© 2008 Wiley Periodicals, Inc. Random Struct. Alg., 2008
Narrations of race in STEM research settings: Identity formation and its discontents
Authors: Malone Kareen Ror , Barabino Gilda 
Published: September 2008

AbstractThis paper discusses conceptions of identity in relation to science education and presents material from a series of interviews and focus groups with graduate students in science and technology. Given difficulties in retention and levels of significant participation by minority students indicated by aggregate data, the issue of race, as it informs critical interactions at a majority research university, is explored in terms of its effects on identity formation. It is argued that we need to look at “real‐time” science to see how subtle interactions affect minority graduate students. These interactions reveal how identity is established through the positioning inside or outside of the laboratory culture. Three themes were explored regarding the tensions of identity formation in the context of race and science education: (1) the issue of isolation, marginalization, and invisibility; (2) being valued through recognition of one's contributions to the community of scientists; and (3) reading race as an additional burden for minority students. Two participants' stories and their positioning as outsiders are explored in detail. The authors contrast building an identity as a scientist through one's educational experiences against being positioned as the “only one” representing his or her race at a primarily White institution. © 2008 Wiley Periodicals, Inc.Sci Ed93:485–510, 2009
Organization governance form in franchising: efficient contracting or organizational momentum?
Authors: Mitsuhashi Hitoshi , Shane Scott , Sine Wesley D. 
Published: September 2008

AbstractWe examine firms' choice of organizational governance form. Using longitudinal data on a sample of business format franchisors operating in North America, we show that the cross‐sectional evidence commonly used to demonstrate support for efficient contracting explanations for organizational governance form is not robust to the year of investigation, firm effects, or selection effects. We theorize that this outcome may result from dynamic processes through which a firm's organizational governance form evolves. We develop and test two hypotheses for the effects of organizational momentum on organizational governance form, and find that organizational momentum is a robust predictor. Our results suggest that researchers consider the dynamics of momentum in explaining the form of firm governance. Copyright © 2008 John Wiley & Sons, Ltd.
The many views of a process: Toward a process architecture framework for product development processes
Authors: Browning Tyson R. 
Published: September 2008

AbstractA product or systemdevelopment processis a kind of complex system, arguably even more complex than the system it produces. Yet, the models and tools used by systems engineers and program managers to plan and manage technical work—such as process flowcharts, Gantt charts, work breakdown structures, and text‐rendered procedures—are less sophisticated and capable than the ones used to design the product system. When used, the various process models are often challenged to incorporate and maintain synchronized program information—e.g., they may be created by different subgroups in a program and based on different assumptions, and they may diverge as a program proceeds. Recently,architecture frameworks(AFs) have been used to help manage the complexity in engineered systems. An AF provides a portfolio ofviewsof a complex system, each of which describes it partially and in a format meaningful to its users and their particular needs. This paper proposes the application of AF concepts to the management of the work done to develop a complex system product. The pieces of work and their relationships constitute a complex process. A portfolio of integrated and synchronized views of a single process model would seem to be preferable to the current state—a number of disparate and uncoordinated management models. This paper introduces a new application of AFs to development processes and suggests this area as one for further research and development in the systems engineering community. © 2008 Wiley Periodicals, Inc. Syst Eng
The Stigmatising Implications of Presenting Schizophrenia as a Genetic Disease
Authors: Bennett Laura , Thirlaway Kathryn , Murray Alexandra J. 
Published: September 2008

AbstractThis study aimed to investigate the hypothesis that belief in a genetic aetiology of schizophrenia will increase the stigma associated with the disorder. Levels of five potentially stigmatising attitudes were compared in two groups of participants who had read a vignette describing an individual who has schizophrenia. In one group the disorder was explained as being caused by ‘genetic’ factors, and in the other by ‘environmental’ factors. This study found that three of the five potentially stigmatising attitudes measured were increased when participants read a vignette with a genetic causation rather than an environmental causation. Firstly, genetic attributions increased levels of associative stigma towards close relatives (p < 0.001). Secondly, participants viewed recovery as less likely when genetic factors were implicated as causative (p < 0.001). Finally, there was also an increased perception of the character's “dangerousness” when the condition was explained by genetic factors (p < 0.05). Contrary to previous research was the finding that perceived aetiology had no effect on participant's desire for social distance from an affected individual. Neither did perceived aetiology influence beliefs about moral accountability. The implications of these findings suggest that genetic counsellors and other health professionals, who are providing genetic information to those affected by schizophrenia should be aware of the possibility that a genetic explanation of schizophrenia could increase potentially stigmatising attitudes towards their clients and their clients’ families. It is also possible that individuals with a diagnosis of schizophrenia may themselves form deterministic interpretations of the genetic information they receive and subsequently be less likely to adopt behavioural advice or adhere to treatment. Counsellors and health professionals should strive to present information in a balanced manner, ensuring recipients understand the multi‐factorial causes of the disease.
Nile floods recorded in deep Mediterranean sediments
Authors: Ducassou Emmanuelle , Mulder Thierry , Migeon Sébastien , Gonthier Eliane , Murat Anne , Revel Marie , Capotondi Lucilla , Bernasconi Stefano M. , Mascle Jean , Zaragosi Sébastien 
Published: September 2008

AbstractClastic mud beds rich in continental organic matter are observed recurrently in the Nile deep-sea turbidite system. They formed during flooding periods of the river similar to those that induce sapropel formation and occurred during periods of increased density stratification of the eastern Mediterranean. The very fine-grained flood deposits are intercalated within pelagic sediments, sapropels and Bouma-type turbidites. These flood deposits form by the successive reconcentrations of surface (hypopycnal) plumes by convective sedimentation, which in turn generate a fine-grained low-energy hyperpycnal flow. Sea-level high stands seem also to favor hypopycnal plume formation and increase clastic mud bed formation. Consequently, these muddy clastic beds provide a direct link between deep-marine sedimentary records and continental climatic change through flood frequency and magnitude.
Au-dessous de Specℤ
Authors: Toën Bertrand , Vaquié Michel 
Published: September 2008

AbstractIn this article we use the theories of relative algebraic geometry and of homotopical algebraic geometry (cf. [HAGII]) to construct some categories of schemes defined under Specℤ. We define the categories of ℕ-schemes, 1-schemes, -schemes, +-schemes and 1-schemes, where (from an intuitive point of view) ℕ is the semi-ring of natural numbers, 1 is the field with one element, is the ring spectra of integers, + is the semi-ring spectra of natural numbers and 1 is the ring spectra with one element. These categories of schemes are linked together by base change functors, and all of them have a base change functor to the category of ℤ-schemes. We show that the linear group Gln and the toric varieties can be defined as objects in these categories.