bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interference control in preschoolers: factors influencing performance on the day–night task
Authors: Montgomery Derek E. , Anderson Maren , Uhl Elizabeth 
Published: January 2008

AbstractTwo experiments investigated preschoolers' interference control in variants of the day–night task. The day–night task involves instructing children across 16 trials to say the word ‘day’ when viewing a card depicting a nighttime sky and to say ‘night’ when shown a picture of the daytime sky. The purpose of the experiments was to investigate whether the depiction on each card distracts children because it is semantically associated with the instructed response or because the depicted item cues the alternative (incorrect) response within the response set. The results in the first study (N=23, M=52.65 months) and second study (N=54, M=50.81 months) indicate that a close semantic relation between the picture and the target response does not pose substantial interference for preschoolers. In contrast, the pictured item poses a significant challenge for preschoolers when it depicts the interfering alternative in the response set. Theoretical implications of these results for the development of interference control are discussed. Copyright © 2008 John Wiley & Sons, Ltd.
Neighborhood hypergraphs of bipartite graphs
Authors: Boros Endre , Gurvich Vladimir , Zverovich Igor 
Published: January 2008

AbstractMatrix symmetrization and several related problems have an extensive literature, with a recurring ambiguity regarding their complexity and relation to graph isomorphism. We present a short survey of these problems to clarify their status. In particular, we recall results from the literature showing that matrix symmetrization is in fact NP‐hard; furthermore, it is equivalent with the problem of recognizing whether a hypergraph can be realized as the neighborhood hypergraph of a graph. There are several variants of the latter problem corresponding to the concepts of open, closed, or mixed neighborhoods. While all these variants are NP‐hard in general, one of them restricted to the bipartite graphs is known to be equivalent with graph isomorphism. Extending this result, we consider several other variants of the bipartite neighborhood recognition problem and show that they all are either polynomial‐time solvable, or equivalent with graph isomorphism. Also, we study uniqueness of neighborhood realizations of hypergraphs and show that, in general, for all variants of the problem, a realization may be not unique. However, we prove uniqueness in two special cases: for the open and closed neighborhood hypergraphs of the bipartite graphs. © 2008 Wiley Periodicals, Inc. J Graph Theory 58: 69–95, 2008
Analytical characterization of microfabricated SU‐8 emitters for electrospray ionization mass spectrometry
Authors: Sikanen Tiina , Tuomikoski Santeri , Ketola Raimo A. , Kostiainen Risto , Franssila Sami , Kotiaho Tapio 
Published: January 2008

AbstractWe present a detailed optimization and characterization of the analytical performance of SU‐8‐based emitters for electrospray ionization mass spectrometry (ESI/MS). The improved SU‐8 fabrication process presented here enhances patterning accuracy and reduces the time and cost of fabrication. All emitters are freestanding and enable sample delivery by both pressure‐driven and spontaneous flows. The optimized emitter design incorporates a sharp, double‐cantilevered tip implemented to the outlet of an SU‐8 microchannel and provides highly sensitive ESI/MS detection. Moreover, the optimized design allows the use of relatively large microchannel dimensions (up to 200 × 50 µm2, w × h) without sacrificing the detection sensitivity. This is advantageous with a view of preventing emitter clogging and enabling reproducible analysis. The measured limits of detection for the optimized emitter design were 1 nM for verapamil and 4 nM for Glu‐fibrinopeptide B with good quantitative linearities between 1 nM and 10 µM (R2 = 0.9998) for verapamil and between 4 nM and 3 µM (R2 = 0.9992) for Glu‐fibrinopeptide B. The measured tip‐to‐tip repeatability for signal intensity was 14% relative standard deviation (RSD) (n = 3; 5 µM verapamil) and run‐to‐run repeatability 4–11% RSD (n = 4; 5 µM verapamil) for all individual emitters tested. In addition, long‐term stability of < 2% RSD was maintained for timescales of 30 min even under free flow conditions. SU‐8 polymer was also shown to be chemically stable against most of the tested electrospray solvents. Copyright © 2008 John Wiley & Sons, Ltd.
The effects of chromium(III) coordination on the dissociation of acidic peptides
Authors: Pu Dan , Vincent John B. , Cassady Carolyn J. 
Published: January 2008

AbstractThe complexes formed between chromium(III) and synthetic acidic peptides were studied by sustained off‐resonance irradiation collision‐induced dissociation (SORI‐CID) in a Fourier transform ion‐cyclotron resonance (FT‐ICR) mass spectrometer equipped with electrospray ionization (ESI). Neutral peptides and peptides containing one, two, and multiple acidic residues were studied. Formation of [M + Cr − 2H]+ occurred for all peptides. Three noteworthy features were found in the CID spectra of [M + Cr − 2H]+. The first is that fewer fragment ions were produced from [M + Cr − 2H]+ than from [M + H]+. The reason may be that multiple coordination between chromium(III) and carboxylate or carbonyl groups hinders the production of fragment ions by continuing to bind pieces of the peptide to chromium(III) after cleavage of bonds within the peptide. The second feature is loss of CO from [M + Cr − 2H]+ and [yn + Cr − H]+. A mechanism involving coordination of chromium(III) with carboxylate groups is proposed to rationalize elimination of CO. The third feature is that chromium(III) is retained in all fragment ions, indicating strong binding of the metal ion to the peptides. The complex [M + 2Cr − 5H]+ is formed as the peptide chain length and number of acidic residues increases. Longer peptides have more sites to coordinate with chromium(III) and more conformational flexibility. In addition, formation of [M + Cr − 2H]+ from AGGAAAA‐OCH3, which has no carboxylic acid groups, suggests that chromium(III) can coordinate with sites on the peptide backbone, albeit in low abundance. In the negative mode, [M + Cr − 4H]− was only found for peptides containing four or more carboxylic acid groups. This is consistent with deprotonated carboxylic acid groups being involved in chromium(III) coordination and with chromium existing in the 3 + state in the gas‐phase ions. Copyright © 2008 John Wiley & Sons, Ltd.
Isomerization of delta‐9‐THC to delta‐8‐THC when tested as trifluoroacetyl‐, pentafluoropropionyl‐, or heptafluorobutyryl‐ derivatives
Authors: Holler Justin M. , Smith Michael L. , Paul Shom N. , Past Marilyn R. , Paul Buddha D. 
Published: January 2008

AbstractFor GC–MS analysis of delta‐9‐tetrahydrocannabinol (delta‐9‐THC), perfluoroacid anhydrides in combination with perfluoroalcohols are commonly used for derivatization. This reagent mixture is preferred because it allows simultaneous derivatization of delta‐9‐THC and its acid metabolite, 11‐nor‐delta‐9‐THC‐9‐carboxylic acid present in biological samples. When delta‐9‐THC was derivatized by trifluoroacetic anhydride/hexafluoroisopropanol (TFAA/HFIPOH) and analyzed by GC–MS using full scan mode (50–550 amu), two peaks (P1 and P2) with an identical molecular mass of 410 amu were observed. On the basis of the total ion chromatogram (TIC), P1 with a shorter retention time (RT) was the major peak (TIC 84%). To identify the peaks, delta‐8‐THC was also tested under the same conditions. The RT and spectra of the major peak (TIC 95%) were identical with that of P1 for delta‐9‐THC. A minor peak (5%) present also correlated well with the latter peak (P2) for the delta‐9‐THC derivative. The fragmentation pathway of P1 was primarily demethylation followed by retro Diels‐Alder fragmentation (M − 15–68, base peak 100%) indicating P1 as a delta‐8‐THC‐trifluoroacetyl compound. This indicated that delta‐9‐THC isomerized to delta‐8‐THC during derivatization with TFAA/HFIPOH. Similar results were also observed when delta‐9‐THC was derivatized with pentafluoropropionic anhydride/pentafluoropropanol or heptafluorobutyric anhydride/heptafluorobutanol. No isomerization was observed when chloroform was used in derivatization with TFAA. In this reaction, the peaks of delta‐8‐THC‐TFA and delta‐9‐THC‐TFA had retention times and mass spectra matching with P1 and P2, respectively. Because of isomerization, perfluoroacid anhydrides/perfluoroalcohols are not suitable derivatizing agents for analysis of delta‐9‐THC; whereas the TFAA in chloroform is suitable for the analysis. Published in 2008 by John Wiley & Sons, Ltd.
Reduction and adduct formation from electrosprayed solutions of porphyrin salts
Authors: Ramos Catarina I. V. , Santana‐Marques M. Graça , Ferrer Correia A. J. , Tomé João P. C. , Alonso Cristina M. , Tomé Augusto C. , Neves M. Graça P. M. S. , Cavaleiro J. A. S. 
Published: January 2008

AbstractThe solutions of four meso‐tetrakis(N‐alkylpyridinium‐4‐yl)porphyrin salts and of the p‐toluenesulfonate salt of meso‐tetrakis(4‐trimethylammoniumphenyl)porphyrin, in methanol, were studied by electrospray mass spectrometry, in order to investigate the influence of the type of counter ion, the length of the substituent N‐alkyl groups of the four (N‐alkylpyridinium‐4‐yl)porphyrins and the presence of an aromatic (alkylpyridinium) or aliphatic (trimethylammonium) nitrogen, in ion formation.In our experimental conditions, adducts with the counter ions were formed only for the meso‐tetrakis(4‐trimethylammoniumphenyl)porphyrin and were not observed for the other porphyrins, even when the counter ion was the same. In contrast, formation of reduced species, such as the [M4+ + e−]3+, [M4+ + 2e−]2+, [M4+ + 4e− + 2H+]2+, and [M4+ + 5e− + 2H+]+ ions was observed only for the (N‐alkylpyridinium‐4‐yl)porphyrins and the appearance of these species is apparently solvent related and may occur via counter ion/solvent adducts. Copyright © 2008 John Wiley & Sons, Ltd.
Sea surface temperature patterns in the Gulf of Guinea: their implications for the spatio‐temporal variability of precipitation in West Africa
Authors: Odekunle Theophilus O. , Eludoyin A. O. 
Published: January 2008

AbstractThis study examined the sea surface temperature (SST) patterns in the Gulf of Guinea (GOG) and discussed their implications for the spatio‐temporal variability of precipitation in West Africa. The SST data spanning over 49 years (1950–1998) at 2° × 2° resolutions were sourced from the archive of the International Research Institute for climate prediction. The specific locations where data were collected to represent the GOG are longitudes 10°W, 8°W, 6°W, 4°W, 2°W, 0° , 2°E, 4°E, 6°E, and 8°E, and latitudes 5°N, 3°N, 1°N, 1°S, 3°S, and 5°S. The results obtained show that the SST in the GOG generally decreases westward and southward, while the reverse of the case holds for its variability values. Detailed observations show that the SST is generally below the latitudinal average and its variability values, above the latitudinal average mainly between longitudes 8°W and 2°E. The results also show that during the period of July‐August‐September, the SST is anomalously colder between longitudes 8°W and 2°E and the West African coastal border and latitude 3°N. This area was observed as constituting the area of the coastal upwelling. The intra‐annual distribution of the SST, as evident along latitudes 3°N and 5°N, shows two main regimes and two transitional periods in between the regimes. The first regime is November to May, and the second, July to September. The first regime transits to the second during the month of June and the second back to the first, during the month of October. The comparative analysis of the first and second half of the period of study indicates that the SST of the GOG has undergone some warming over time. The comparison also shows that although the SST has generally risen, an area of relatively cool SST near the Guinea coast has expanded from longitudes 7°W–0°W to 8°W–3°E. Copyright © 2008 Royal Meteorological Society
An automated sea breeze selection technique based on regional sea‐level pressure difference: WeMOi
Authors: Azorin‐Molina Cesar , Lopez‐Bustins Joan‐Albert 
Published: January 2008

AbstractA recently defined regional teleconnection pattern for the western Mediterranean basin (western Mediterranean Oscillation, WeMO) has allowed an objective quantification of the synoptic circulation factor on the occurrence of sea breezes. The associated WeMO index (WeMOi) can be used as an initial objective filter for selecting ideal surface pressure conditions for sea breeze development. Applying this filter to the sea breeze database created for Alicante (reference synoptic station) and performing a manual selection method for the 2‐year period (1999–2000), we confirmed the potential use of this objective primary criterion. We used wind speed (WS) and direction (WD) data from 9 coastline meteorological stations to assess the WeMOi applicability to the Iberian Mediterranean coast and the Balearic Isles. The [−1, 1] threshold interval of the daily WeMOi was seen to be a good proxy for detecting weak pressure gradients at surface level. Observational and numerical sea breeze studies require quality databases in order to analyse in depth the main characteristics and physical processes controlling sea breezes. This automated selection technique enabled us to improve the accuracy and processing time of the filter methods for finding sea breeze days by adding a new objective criterion. This new threshold technique [−1, 1], based on regional sea‐level pressure (SLP) difference, is adaptable to any coastal region at mid‐latitudes where a regional barometric dipole can be defined. A regional teleconnection pattern, such as the WeMOi, could be used as a suitable tool for forecasting sea breeze occurrence. Copyright © 2008 Royal Meteorological Society
Micro‐Raman and particle‐induced X‐ray emission spectroscopy for the study of pigments and degradation products present in 17th century coloured maps
Authors: Mendes Nuno , Lofrumento C. , Migliori A. , Castellucci E. M. 
Published: January 2008

AbstractThree different maps of the 17th century, two of them of Portugal and the third of the Iberian Peninsula, all of them hand coloured and of Dutch manufacture (copper engraving), were studied in this work. The study was carried out by using particle‐induced X‐ray emission (PIXE) and micro‐Raman spectroscopy. These are two non‐destructive techniques that provide complementary information on the composition of the materials: PIXE giving elemental information and Raman providing information at a molecular level. By means of the two techniques it has been possible to identify the inorganic pigments used in the three maps, as well as some products of degradation whose causes are not completely understood yet. This article contributes to a better knowledge of the techniques and palettes used for the colouring of maps of this period as well as the degradations of the pigments. Particular attention is given to the presence of a copper oxalate found in two different maps, its presence being associated with green coloured areas and indicating a degradation of a copper‐based green pigment. Copyright © 2008 John Wiley & Sons, Ltd.
Micro‐Raman and fluorescence spectroscopy for the assessment of the effects of the exposure to light on films of egg white and egg yolk
Authors: Osticioli Iacopo , Nevin Austin , Anglos Demetrios , Burnstock Aviva , Cather Sharon , Becucci Maurizio , Fotakis Costas , Castellucci Emilio 
Published: January 2008

AbstractIn this work, non‐destructive techniques were employed for the spectrofluorimetric and micro‐Raman differentiation of solid films of egg yolk and egg white as a function of exposure to light. Using both techniques it is possible to discriminate between the samples on the basis of composition and follow some chemical changes involved during the light‐ageing of egg proteins and fatty acid esters. In egg white, fluorescence emission spectra highlighted the presence of multiple fluorophores, with an effective broadening of the fluorescence emissions following light exposure, ascribed to the partial oxidation and depletion of tryptophan; in the Raman spectrum of dark‐aged egg white a peak at 758 cm−1 is ascribed to the vibrational mode of tryptophan, which is completely absent in the spectrum of samples exposed to light. Changes in the fluorescence of egg yolk following exposure to light are ascribed to the degradation of amino acids, cross‐linking between amino acids and the formation of oxygenated triacylglycerides. These results are corroborated with Raman spectra of the light‐exposed samples, which are associated with wavenumber shifts with respect to the dark‐aged sample for the Amide I and for the characteristic carbonyl vibration at 1744 cm−1 ascribed to the oxidation of fatty acid esters. Copyright © 2008 John Wiley & Sons, Ltd.
New Polyolefin‐Nanocomposites by In Situ Polymerization with Metallocene Catalysts
Authors: Scharlach Katrin , Kaminsky Walter 
Published: January 2008

AbstractSummary: Polypropylene‐nanocomposites were prepared by in‐situ polymerization with the catalysts systems rac[Et(IndH4)2]ZrCl2, Me2Si(Flu)(Ind)ZrCl2 and rac[Me2Si(2‐Me‐4‐(1‐Naph)Ind)2]ZrCl2. The type and size of the nanoparticles and the concentration of the propene were varied. The activity is independent of the type and the size of the filler. It was observed that the filler contents in the polypropylene‐nanocomposites depend on the catalysts system used. The morphology results using TEM revealed that the nanoparticles are uniformly distributed in the isotactic polypropylene matrix. Additionally, the melting points, glass temperatures and crystallization temperatures changed with the amount of the fillers.
Applications of Calixarenes in Polymer Synthesis
Authors: Zhu Weipu , Gou Pengfei , Shen Zhiquan 
Published: January 2008

AbstractSummary: The applications of calixarenes in polymer synthesis have been reviewed. Calixarenes have been used as ligands to prepare rare earth calixarene complexes. A series of rare earth calixarene complexes have been synthesized and employed as efficient catalysts for the polymerization of ethylene, styrene, butadiene, propylene oxide, styrene oxide, trimethylene carbonate, and 5,5‐dimethyl trimethylene carbonate. On the other hand, the synthesis and characterization of star‐shaped polymers with calixarene as core molecules are also described.
Preparation of Poly(amic acid) and Polyimide via Microwave‐Assisted Polycondensation of Aromatic Dianhydrides and Diamines
Authors: Li Quantao , Yang Xiaojin , Chen Wenqiu , Yi Changfeng , Xu Zushun 
Published: January 2008

AbstractSummary: A copolycondesation‐type poly (amic acid) (PAA) was synthesized using pyromellitic dianhydride (PMDA) and 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride (BTDA) as dianhydride monomers, and 4,4′‐oxydianiline (ODA) as a diamine monomer under microwave irradiation in dimethylformamide (DMF). PAA was then converted into a polyimide (PI) by an imidization. The structure and performance of the polymer were characterized by Fourier‐transform infrared (FT‐IR) spectroscopy, Proton nuclear magnetic resonance (1H NMR) spectrometry, viscosity, X‐ray diffraction (XRD), and thermogravimetric (TG) analyses. The results showed that under microwave irradiation, the intrinsic viscosity and the yield of PAA were increases, and the reaction time was shortened. The FT‐IR spectra of the polymer revealed characteristic peaks for PI around 1778– and 1723 cm–1. TG curves indicated that the obtained PI began to lose weight at 535 °C, and its 10% thermal decomposition temperature under N2 was 587 °C.
Tuning Macromolecular Structures of Synthetic Vectors for Gene Therapy
Authors: Cheradame H. , Sassatelli M. , Pomel C. , Sanh A. , Gau‐Racine J. , Bacri L. , Auvray L. , Guégan P. 
Published: January 2008

AbstractSummary: The synthesis of triblocks poly(2‐methyl‐2‐oxazoline‐b‐tetrahydrofurane‐b‐2‐methyl‐2‐oxazoline) has been developed. It was shown that the technique of polymerization of the second block from the living species created on the two chain ends of poly(THF) is successful but makes the control of the size of the poly(THF) block difficult due a fast depolymerization upon the introduction of the second monomer. A purification technique was used to get rid of the possible homopoly(2‐methyl‐2‐oxazoline) formed. Various analytical techniques were used to characterize the behavior of the triblock and more particularly in the presence of DNA. Electrophoresis on agarose gels and neutron scattering, demonstrated that the neutral triblock does not appreciably interact with DNA. It was also shown that the triblock for which approximately half (47%) of the methyloxazoline units were transformed into ethylenimine units by hydrolysis gives only loose interactions with DNA. This result is assigned to the fact that charge density plays a major role in the interactions of positive polyelectrolytes with the negatively charged DNA. The triblock was shown being able to interact with bilayer lipid membranes mimicking cell membranes. The efficiency of the hydrolysed triblock was much higher, while the size of holes created in the membranes is not large enough to give passage to DNA.
Numerical stabilization of Biot's consolidation model by a perturbation on the flow equation
Authors: Aguilar G. , Gaspar F. , Lisbona F. , Rodrigo C. 
Published: January 2008

AbstractIn this paper a stabilized finite element scheme for the poroelasticity equations is proposed. This method, based on the perturbation of the flow equation, allows us to use continuous piecewise linear approximation spaces for both displacements and pressure, obtaining solutions without oscillations independently of the chosen discretization parameters. The perturbation term depends on a parameter which is established in terms of the mesh size and the properties of the material. In the one‐dimensional case, this parameter is shown to be optimal. Some numerical experiments are presented indicating the efficiency of the proposed stabilization technique. Copyright © 2008 John Wiley & Sons, Ltd.
Recent advances in plant cell wall proteomics
Authors: Jamet Elisabeth , Albenne Cécile , Boudart Georges , Irshad Muhammad , Canut Hervé , Pont‐Lezica Rafael 
Published: January 2008

AbstractThe plant extracellular matrix contains typical polysaccharides such as cellulose, hemicelluloses, and pectins that interact to form dense interwoven networks. Plant cell walls play crucial roles during development and constitute the first barrier of defense against invading pathogens. Cell wall proteomics has greatly contributed to the description of the protein content of a compartment specific to plants. Around 400 cell wall proteins (CWPs) of Arabidopsis, representing about one fourth of its estimated cell wall proteome, have been described. The main points to note are that: (i) the diversity of enzymes acting on polysaccharides suggests a great plasticity of cell walls; (ii) CWPs such as proteases, polysaccharide hydrolytic enzymes, and lipases may contribute to the generation of signals; (iii) proteins of unknown functions were identified, suggesting new roles for cell walls. Recently, the characterization of PTMs such as N‐ and O‐glycosylations improved our knowledge of CWP structure. The presence of many glycoside hydrolases and proteases suggests a complex regulation of CWPs involving various types of post‐translational events. The first 3‐D structures to be resolved gave clues about the interactions between CWPs, or between CWPs and polysaccharides. Future work should include: extracting and identifying CWPs still recalcitrant to proteomics, describing the cell wall interactome, improving quantification, and unraveling the roles of each of the CWPs.