bluuebunny/crossref_metadata_2025_split huggingface dataset:
Differential Pulse Voltammetric Determination of Selenocystine Using Selenium‐gold Film Modified Electrode
Authors: Bai Yan , Yan Xiaoli , Li Rui , Zheng Wenjie , Yang Fang 
Published: June 2005

AbstractDifferential pulse voltammetric determination of selenocystine (SeC) using selenium‐gold film modified glassy carbon electrode ((Se‐Au)/GC) is presented. In 0.10 mol⋅L−1 KNO3 (pH 3.20) solution, SeC yields a sensitive reduction peak at −740 mV on (Se‐Au)/GC electrode. The peak current has a linear relationship with the concentration of SeC in the range of 5.0×10−8–7.0×10−4 mol⋅L−1, and a 3σ detection limit of SeC is 3.0×10−8 mol⋅L−1. The relative standard deviation of the reduction current at SeC concentration of 10−6 mol⋅L−1 is 3.88% (n=8) using the same electrode, and 4.19% when using three modified electrodes prepared at different times. The content of SeC in the selenium‐enriched yeast and selenium‐enriched tea is determined. The total selenium in ordinary or selenium‐enriched tea is determined by DAN fluorescence method. The results indicate that in selenium‐enriched yeast about 20% of total selenium is present as SeC and in selenium‐enriched tea SeC is the major form of selenoamino acids. The total selenium content in selenium‐enriched tea soup is 0.09 μgSe/g accounting by 7% compared with that in selenium‐enriched tea. Hence, only a little amount of selenium is utilized by drinking tea, and most selenium still stay in tealeaf. Uncertainty are 22.4% and 16.1% for determination of SeC in selenium‐enriched yeast and selenium‐enriched tea by differential pulse voltammetry (DPV) on (Se‐Au)/GC electrode, respectively.
Shaking table tests on reinforced concrete frames without and with passive control systems
Authors: Dolce Mauro , Cardone Donatello , Ponzo Felice C. , Valente Claudio 
Published: June 2005

AbstractAn extensive experimental program of shaking table tests on reduced‐scale structural models was carried out within the activities of the MANSIDE project, for the development of new seismic isolation and energy dissipation devices based on shape memory alloys (SMAs). The aim of the experimental program was to compare the behaviour of structures endowed with innovative SMA‐based devices to the behaviour of conventional structures and of structures endowed with currently used passive control systems.This paper presents a comprehensive overview of the main results of the shaking table tests carried out on the models with and without special braces. Two different types of energy dissipating and re‐centring braces have been considered to enhance the seismic performances of the tested model. They are based on the hysteretic properties of steel elements and on the superelastic properties of SMAs, respectively.The addition of passive control braces in the reinforced concrete frame resulted in significant benefits on the overall seismic behaviour. The seismic intensity producing structural collapse was considerably raised, interstorey drifts and shear forces in columns were drastically reduced. Copyright © 2005 John Wiley & Sons, Ltd.
Seismic demand sensitivity of reinforced concrete shear‐wall building using FOSM method
Authors: Lee Tae‐Hyung , Mosalam Khalid M. 
Published: June 2005

AbstractThe uncertainty in the seismic demand of a structure (referred to as the engineering demand parameter, EDP) needs to be properly characterized in performance‐based earthquake engineering. Uncertainties in the ground motion and in structural properties are responsible for EDP uncertainty. In this study, sensitivity of EDPs to major uncertain variables is investigated using the first‐order second‐moment method for a case study building. This method is shown to be simple and efficient for estimating the sensitivity of seismic demand. The EDP uncertainty induced by each uncertain variable is used to determine which variables are most significant. Results show that the uncertainties in ground motion are more significant for global EDPs, namely peak roof acceleration and displacement, and maximum inter‐storey drift ratio, than those in structural properties. Uncertainty in the intensity measure (IM) of ground motion is the dominant variable for uncertainties in local EDPs such as the curvature demand at critical cross‐sections. Conditional sensitivity of global and local EDPs given IM is also estimated. It is observed that the combined effect of uncertainties in structural properties is more significant than uncertainty in ground motion profile at lower IM levels, while the opposite is true at higher IM levels. Copyright © 2005 John Wiley & Sons, Ltd.
EEG alpha synchronization and functional coupling during top‐down processing in a working memory task
Authors: Sauseng Paul , Klimesch Wolfgang , Doppelmayr Michael , Pecherstorfer Thomas , Freunberger Roman , Hanslmayr Simon 
Published: May 2005

AbstractElectroencephalogram (EEG) α (around 10 Hz) is the dominant rhythm in the human brain during conditions of mental inactivity. High amplitudes as observed during rest usually diminish during cognitive effort. During retention of information in working memory, however, power increase of α oscillations can be observed. This α synchronization has been interpreted as cortical idling or active inhibition. The present study provides evidence that during top‐down processing in a working memory task, α power increases at prefrontal but decreases at occipital electrode sites, thereby reaching a state in which α power and frequency become very similar over large distances. Two experimental conditions were compared. In the first, visuospatial information only had to be retained in memory whereas the second condition additionally demanded manipulation of the information. During the second condition, stronger α synchronization at prefrontal sites and larger occipital α suppression was observed as compared to that for pure retention. This effect was accompanied by assimilation of prefrontal and occipital α frequency, stronger functional coupling between prefrontal and occipital brain areas, and α latency shifts from prefrontal cortex to primary visual areas, possibly indicating the control of posterior cortical activation by anterior brain areas. An increase of prefrontal EEG α amplitudes, which is accompanied by a decrease at posterior sites, thus may not be interpreted in terms of idling or “global” inhibition but may enable a tight functional coupling between prefrontal cortical areas, and thereby allows the control of the execution of processes in primary visual brain regions. Hum Brain Mapp, 2005. © 2005 Wiley‐Liss, Inc.
The emergence of the unmarked: A new perspective on the language‐specific function of Broca's area
Authors: Grewe Tanja , Bornkessel Ina , Zysset Stefan , Wiese Richard , von Cramon D. Yves , Schlesewsky Matthias 
Published: May 2005

AbstractA number of neuroimaging studies have implicated an involvement of Broca's area, particularly of the pars opercularis of the left inferior frontal gyrus (IFG), in the processing of complex (permuted) sentences. However, functional interpretations of this region's role range from very general (e.g., in terms of working memory) to highly specific (e.g., as supporting particular types of syntactic operations). A dissociation of these competing accounts is often impossible because in most cases, the language internal complexity of permuted sentence structures is accompanied invariably by increasing costs of a more general cognitive nature (e.g., working memory, task difficulty, and acceptability). We used functional magnetic resonance imaging to explore the precise nature of the pars opercularis activation in the processing of permuted sentences by examining the permutation of pronouns in German. Although clearly involving a permutation operation, sentences with an initial object pronoun behave like simple, subject‐initial sentences (e.g., in terms of acceptability) because of a rule stating that pronouns should generally precede non‐pronominal arguments. The results of the experiment show that in contrast to non‐pronominal permutations, sentences with a permuted pronoun do not engender enhanced pars opercularis activation. Our findings therefore speak against both language‐related working memory and transformation‐based accounts of this region's role in sentence comprehension. Rather, we argue that the pars opercularis of the left IFG supports the language‐specific linearization of hierarchical linguistic dependencies. Hum Brain Mapp, 2005. © 2005 Wiley‐Liss, Inc.
Characterizing modulatory interactions between areas V1 and V2 in human cortex: A new treatment of functional MRI data
Authors: Friston K. J. , Ungerleider L. G. , Jezzard P. , Turner R. 
Published: May 2005

AbstractReversible cooling experiments in monkey visual cortex have demonstrated that visually driven neuronal activity in V2 depends on feedforward projections from V1, whereas neuronal activity in V1 is modulated by feedback, or reentrant, projections from V2. We present evidence for a homologous asymmetry in reciprocal connections between V1 and V2 in human cortex using physiological measurements obtained with functional MRI. The analysis was based on a nonlinear model of effective connectivity that partitioned the influence that one region exerted over another into an obligatory effect (an effect that depended only on the input) and a modulatory effect (an effect that represented an interaction between input and activity intrinsic to the target region). Using estimates of the modulatory effect we tested two related hypotheses: (1) that V2 would be a major source of modulatory influences on V1; and (2) that the modulatory effects of V2 on V1 would be greater than those of V1 on V2. The first constitutes a hypothesis about the regional or topographic organization of (modulatory) effective connectivity and the second hypothesis directly addresses the functional asymmetry suggested by reversible cooling experiments. The results confirmed that the origins of feedback modulatory effects on V1 were regionally specific and most pronounced in V2. In contrast, feedforward modulatory influences on V1 on V2 were negligible. This apparent asymmetry between feedforward and feedback modulatory interactions was evident in both hemispheres and appears to be a fairly robust feature of nonlinear interactions between striate and extrastriate cortex. © 1995 Wiley‐Liss, Inc.
Synthetic PET: Analyzing large‐scale properties of neural networks
Authors: Arbib M. A. , Bischoff A. , Fagg A. H. , Grafton S. T. 
Published: May 2005

AbstractSynthetic PET is introduced as a new computational technique for connecting neural network studies based on animal data and image studies of human brain function. Synthetic PET comparisons are taken from a computational model of interacting neural networks in, for example, the monkey brain by integrating synaptic activity in each subnetwork as different simulated tasks are performed. Given a pair of tasks, comparative synaptic activity levels for each modeled neural region are then painted into the homologous regions of a three‐dimensional model of the human brain corresponding to the Talairach atlas. The resulting comparison then offers predictions of relative changes of neuronal activity as obtained from PET comparisons of humans performing a similar pair of tasks. Where neurophysiological data and individual arrays of neural networks give us a very fine‐grained view of the behavior of just a few neurons within nonhumans, PET measures provide a more global view of brain function. Synthetic PET allows us to integrate human and monkey studies in the construction of more complete models of the neural mechanisms used by both species in similar tasks. The technique is demonstrated in a saccade generation task. The method readily generalizes to other forms of brain imaging. © 1995 Wiley‐Liss, Inc.
Automatic 3‐D model‐based neuroanatomical segmentation
Authors: Collins D. Louis , Holmes C. J. , Peters T. M. , Evans A. C. 
Published: May 2005

AbstractExplicit segmentation is required for many forms of quantitative neuroanatomic analysis. However, manual methods are time‐consuming and subject to errors in both accuracy and reproducibility (precision). A 3‐D model‐based segmentation method is presented in this paper for the completely automatic identification and delineation of gross anatomical structures of the human brain based on their appearance in magnetic resonance images (MRI).The approach depends on a general, iterative, hierarchical non‐linear registration procedure and a 3‐D digital model of human brain anatomy that contains both volumetric intensity‐based data and a geometric atlas. Here, the traditional segmentation strategy is inverted: instead of matching geometric contours from and idealized atlas directly to the MRI data, segmentation is achieved by identifying the non‐linear spatial transformation that best maps corresponding intensity‐based features between a model image and a new MRI brain volume. When completed, atlas contours defined on the model image are mapped through the same transformation to segment and label individual structures in the new data set.Using manually segmented sturcture boundaries for comparison, measures of volumetric difference and volumetric overlap were less than 2% and better than 97% for realistic brain phantom data, and less than 10% and better than 85%, respectively, for human MRI data. This compares favorably to intra‐observer variability estimates of 4.9% and 87%, respectively. The procedure performs well, is objective and its implementation robust. The procedure requires no manual intervention, and is thus applicable to studies of large numbers of subjects. The general method for non‐linear image matching is also useful for non‐linear mapping of brain data sets into stereotaxic space if the target volume is already in stereotaxic space. © 1995 Wiley‐Liss, Inc.
Characterization of acylcarnitines using fast atom bombardment mass spectrometry and gas chromatography/mass spectrometry
Authors: Van Bocxlaer J. F. , Claeys M. , Van Den Heuvel H. , De Leenheer A. P. 
Published: May 2005

AbstractMass spectral data are reported for an extended series of synthesized acylcarnitines. Direct mass spectrometry was performed using ionization by fast atom bombardment in combination with high‐energy collisional activation and B/E linked scanning. The data show that it is possible to distinguish between isomeric compounds using this technique. Gas chromatographic/mass spectrometric analysis data for acylcarnitines, as their acyloxylactone derivatives, are reported. Both electron impact and chemical ionization modes were used, permitting the unequivocal characterization and identification of the various compounds. In view of the recent marked increase in acylcarnitine profiling activities, the comprehensively reported mass spectrometric and gas chromatographic data may be useful for reference purposes.
Abstraction of multiple surface atoms by pyrazine, pyrene and HC2N ions on low‐energy collisions with self‐assembled monolayer surfaces
Authors: Riederer Donald E. , Cooks R. Graham , Linford Matthew R. 
Published: May 2005

AbstractIon/surface reactions of pyrazine and pyrene molecular ions and the HC2N+· ion were investigated using an alkyl self‐assembled monolayer surface consisting of hydrogenated and perdeuterated chains (CH3(CH2)15S–Au and CD3(CD2)15S–Au) intimately mixed in a 1:1 ratio. Each of these projectile ions is known to react upon collision at hydrocarbon‐covered surfaces, HC2N+· by abstraction of multiple hydrogen atoms and the pyrazine and pyrene molecular ions by abstraction of groups containing one or more carbon atoms. Data from the isotopically mixed surface show that pyrazine and pyrene abstract multiple carbon units from a single chain and that the units are transferred as intact alkyl units. The isotopic peak pattern arising from addition of two hydrogens to the HC2N+· ion on collision with the mixed surface differs from that expected from random addition of H and D, and the results indicate that multiple hydrogen atoms are abstracted from the same surface chain. Translational energy measurements on the ion/surface reaction products show that they leave the surface with very low kinetic energies (<5 eV).
Ionization processes in matrix‐assisted laser desorption/ionization mass spectrometry: Matrix‐dependent formation of [M + H]+ vs [M + Na]+ ions of small peptides and some mechanistic comments
Authors: Liao Pao‐Chi , Allison John 
Published: May 2005

AbstractThe relative signal intensities of [M + H]+ vs [M + Na]+ ions of some small peptides were found to be highly matrix‐dependent in matrix‐assisted laser desorption/ionization (MALDI) experiments when sinapinic acid, α‐cyano‐4‐hydroxycinnamic acid and 2,5‐dihydroxybenzoic acid were used as matrices. Presumably, this observation results from the competition of two different mechanisms for the ionization steps. Possible mechanisms for the formations of [M + H]+ and [M + Na]+ ions are proposed and discussed in the pursuit of defining the ionization step in MALDI. Several experiments were designed and performed for the further refinement of the mechanism. The results suggest that proton transfer from a matrix molecule to an analyte plays an important role in the ionization step. The transferring proton may be derived from photoionized or electronically excited matrix molecules. In contrast, some data are most consistent with a gas‐phase mechanism for [M + Na]+ ions.
Human α‐fetoprotein produced from hep G2 cell line: Structure and heterogeneity of the oligosaccharide moiety
Authors: Ferranti Pasquale , Pucci Pietro , Marino Gennaro , Fiume Immacolata , Terrana Benedetto , Ceccarini Costante , Malorni Antonio 
Published: May 2005

AbstractThe carbohydrate moiety of human α‐fetoprotein, an RMM 67000 glycoprotein produced in a hepatoma cell line (Hep G2), was investigated by the combined use of high‐resolution chromatographic techniques and mass spectrometry. Fast atom bombardment mass spectrometric (FABMS) and reversed‐phase high‐performance liquid chromatographic analysis of α‐fetoprotein obtained from a large‐scale cell culture following tryptic and peptide N‐glycanase F hydrolysis demonstrated that the protein contains a single glycosylation site at level of asparagine 232. Further, electrospray mass spectrometric measurement of the intact protein molecular mass showed that two main glycoforms are present. The complete definition of the structural heterogeneity of the oligosaccharide moiety was achieved by high‐performance anion‐exchange chromatography with pulsed amperometric detection together with carbohydrate mapping by FABMS of the released oligosaccharides demonstrating (i) that the glycosylation produced by cell culture is of the biantennary complex type typical of human hepatoma α‐fetoprotein and (ii) the presence of two main structures in a ratio of about 2:1 differing in the presence of a fucose residue in the N‐acetylglucosamine in the non reducing portion of the molecule.
Assay of the concentration and stable isotope enrichment of short‐chain fatty acids by gas chromatography/mass spectrometry
Authors: Powers Lisa , Osborn Melissa K. , Yang Dawei , Kien C. Lawrence , Murray Robert D. , Beylot Michel , Brunengraber Henri 
Published: May 2005

AbstractIsotope dilution gas chromatographic mass spectrometric assays were developed for the concentration of shortchain fatty acids and of lactate in plasma. The assays involve spiking the samples with 2H‐ and/or 13‐C‐labeled internal standards and direct derivatization with 2,4‐difluoroaniline, using 1,3‐dicyclohexylcarbodiimide as a coupling agent. The assay can be used to determine the isotopic enrichment or mass isotopomer distribution of the fatty acids and of lactate. Blanks by ubiquitous formate, acetate and lactate are minimized by the one‐step derivatization procedure without deproteinization, using reagents dissolved in hydrocarbons. The assays were applied to experiments conducted in live dogs, pigs and monkeys, and in perfused rat livers. These techniques, in conjunction with appropriate stable isotope models, can be used to study carbohydrate fermentation in humans, ruminants and non‐ruminant mammals.
Fast atom bombardment mass spectra of dihydroxybenzenes: Formation of radical cation adduct between sample and matrix
Authors: Madhusudanan K. P. 
Published: May 2005

AbstractUnder fast atom bombardment, dihydroxybenzenes form predominantly the M+· and [M + Matrix]+· ions. The second field‐free region metastable decomposition of the [M + Matrix]+· ion involves the loss of a neutral molecule of the matrix. In the case of the hydroquinone–matrix adduct ion, elimination of both the matrix and hydroquinone are observed. Surprisingly, alkali metal cationization also leads to the formation of abundant radical cations in which the acidic hydrogens have been replaced with alkali metal. The degree of this exchange varies among the isomeric compounds. The facile formation of radical cations and their adducts appears to be due to various factors such as the ionization potentials, redox potentials and the proton affinities of the dihydroxybenzenes and the analyte‐matrix interactions.
Studies of the MALDI process by luminescence spectroscopy
Authors: Ehring Hanno , Sundqvist Bo U. R. 
Published: May 2005

AbstractThe process of matrix‐assisted laser desorption/ionization (MALDI) was investigated by studying the luminescence of matrix molecules induced by laser radiation. An optical multi‐channel analyser was utilized for the analysis of luminescence. The luminescence spectra of several MALDI matrices in the solid and liquid phase, the intensity and shape of the spectra at different temperatures, the intensity of the emitted light as a function of the laser fluences and the kinetics of the luminescence were investigated. Measurements of 2,5‐dihydroxybenzoic acid and ferulic acid at different temperatures allow the estimation of the average luminescence quantum yield, which is less than 0.2 at room temperature and the ionization threshold laser fluence. The low yield means that only a minor part of the absorbed energy is emitted. The major part of photon energy absorbed by the molecules relaxes by internal conversion and therefore contributes to the desorption/ionization process. At lower temperatures, the quantum yield increases significantly, which can explain the previously observed increase in the threshold fluence at lower temperatures. Time‐resolved measurements and the shape of the spectra indicate that the molecules investigated form excimers by laser irradiation. At laser fluences around the desorption threshold the luminescence is quenched, presumably by S1–S1 annihilation processes and/or phase transitions. The annihilation processes demonstrate that the electronically excited states are very mobile and interact with each other even at low exciton densities, i.e. laser fluences far below the ionization threshold laser fluence. The mobility can explain ion formation at laser fluences where two‐photon ionization in the gas phase is improbable. At low temperatures the quenching starts at lower laser fluences, which can be explained by the longer lifetimes of the excitons at these temperatures making interactions more probable. No long‐lived excited states, i.e. delayed fluoresecence or phosphorescence, were detected for 2,5‐dihydroxybenzoic acid and ferulic acid, whereas 3‐hydroxypicolinic acid emits photons up to 100 μs after the laser pulse.