bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ionization process of the hydrogen atom in intense laser fields: Non–Born‐Oppenheimer 1D model calculations
Authors: Ohta Yasuhito , Maki J. , Nagao Hidemi , Nishikawa Kiyoshi 
Published: February 2004

AbstractThe ionization process of the hydrogen atom in two‐color laser field is investigated based on non–Born‐Oppenheimer one‐dimensional model. In this model, both electron and nucleus are described by the time‐dependent Hartree equations. By numerically solving the equations, the influence of the relative phase ϕ of the laser field with the spatial distribution of electron and nucleus is investigated. For ϕ = 0, the electron is moved to the direction in which the maximum of the asymmetric combined electric field pointed. For ϕ = π/2, the electron is shown to be pulled in the opposite direction. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Expansion(s) of r
Authors: Harris Frank E. 
Published: February 2004

AbstractThe expansion for r claimed by Lüchow and Kleindienst to be “new” is shown to be algebraically identical to that reported some years previously by Pauli and Kleindienst but with the coefficients of the expansion brought to a far more convenient form. The demonstration presented here also reveals some previously unreported relationships connecting these coefficients. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Antioxidant activity of flavonols
Authors: Ghiotto R. C. T. , Lavarda F. C. , Ferreira F. J. B. 
Published: February 2004

AbstractIn this work we use a single new electronic index to describe the antioxidant activity of the flavonols, a special class of flavonoids. We also try to predict theoretically the antioxidant activity of some yet nonisolated flavonols. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Tunneling through a fluctuating barrier in the presence of a periodically driving field
Authors: Saha Aparna , Sarkar Pranab 
Published: February 2004

AbstractThe zero and finite temperature tunneling dynamics of a periodically driven particle moving in a bistable potential with a fluctuating barrier is studied. We have focused on the influence of barrier fluctuation and thermal modulation on the tunneling processes in the presence of a driving field. At zero temperature, for a fixed strength of the driving field, both the tunneling probability and rate passes through a well‐defined minimum when plotted as a function of fluctuation frequency while it reveals a clear maximum as a function of driving frequency. However, at T > 0 the tunneling probability and rate show two maxima as a function of both fluctuation frequency and driving frequency. In both zero and finite temperature, the tunneling rate constant decreases with increasing fluctuation strength. So, the barrier fluctuation may enhance the stability of a periodically driven system. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Role of resonances in building collision cross‐sections: Mittag‐Leffler‐based study
Authors: Alferova Tatjana , Elander Nils 
Published: February 2004

AbstractThe method of complex dilation is used to define the partial wave S‐matrix in the sector of the fourth quadrant of the complex energy plane. Two ways of obtaining the expansion coefficients—the partial wave S‐matrix residues—are studied. The Mittag‐Leffler decomposition of the partial wave S‐matrix as a sum of residue terms and an integral contribution is used to define the contributions of a number of the partial wave S‐matrix poles, related to a 1‐D potential, to the corresponding S‐wave cross‐section. The obtained expansion demonstrates a way of describing the contribution from a single pole to the partial wave S‐matrix and thereby to various types of cross‐sections. Our model study shows how peaks in a cross‐section not only can be attributed to so‐called isolated resonances but also to a set of overlapping barrier‐type resonances. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Construction of unique canonical coefficients for antisymmeterized geminal power states
Authors: Weiner B. , Ortiz J. V. 
Published: February 2004

AbstractCoefficients often defined to be canonical for a given geminal may not be unique. In this article we show by carefully examining a theorem by B. Zumino how to construct unique canonical coefficients for a geminal. This result leads to expansions of antisymmeterized geminal power states solely in terms of natural generalized spin orbitals and positive geminal occupation numbers. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Polynitrogen clusters containing five‐membered rings
Authors: Cheng Li Ping , Li Se , Li Qian Shu 
Published: February 2004

AbstractPossible structures of N15 cluster were examined by ab initio (MP2) and density functional theory (DFT) methods with the 6‐31G* basis set. Their stabilities were compared together with other polynitrogen clusters Nn (n = 8, 10–14) reported in the literature. The order of stability was made respectively according to even or odd numbers of the total nitrogen atoms in clusters. It is found that both for even‐numbered clusters N2n (n = 4–7) and odd‐numbered clusters N2n + 1 (n = 5–7) the thermodynamically most stable isomers are all based on pentazole units; for each one of Nn (n = 8, 10–15) clusters, the more conjugated the five‐membered ring the more stable is the isomer; and, the more side‐chains the N5 ring links the less stable is the isomer. Another finding is that the larger the cluster the less stable is the cluster for every series of clusters of (a) containing two five‐membered rings with an even number of total nitrogen atoms [N10 (D2d), N12 (C2h), N14 (C2h)], (c) containing one five‐membered ring and a side‐chain with an even number of total nitrogen atoms [N8 (CS), N10 (CS), N12 (CS), N14 (CS)], (d) containing one five‐membered ring and a side‐chain with an odd number of total nitrogen atoms [N11 (CS), N13 (CS), N15 (CS)], (e) chain clusters with an even number of total nitrogen atoms [N8 (C2h), N10 (C2h), N12 (C2h), N14 (C2h)], and (f) chain clusters with an odd number of total nitrogen atoms [N11 (C2v), N13 (C2v), N15 (C2v)]. For another series of clusters with two five‐membered ring units [N11 (C2), N13 (C2v), and N15 (C2v)] (series b) the N13 (C2v) shows the best stability. It is also found that the even‐numbered nitrogen clusters are more stable than the odd‐numbered ones in comparison of series (a) with (b), (c) with (d), and (e) with (f). © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Quantum interference effects in the Br2 electronic predissociation: Dependence upon the molecular properties
Authors: Farias Patricia M. A. , Longo Ricardo L. 
Published: February 2004

AbstractThe occurrence of quantum interference in the Br2 electronic predissociation has been observed for the first time. It is also shown that the quantum interference effects are strongly dependent upon the representation of the molecular properties, such as the kinetic coupling and the transition dipole moment. The fast Fourier transform method implemented within the wave packet formalism was used to simulate the time evolution of the molecular system under the influence of single monochromatic ultrashort laser pulses. The quantum interference has been inferred from the oscillatory behavior of the autocorrelation functions, which have also been used to calculate the cross‐sections, the branching ratios, and the selectivity. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Key fragmentation patterns of aporphine alkaloids by electrospray ionization with multistage mass spectrometry
Authors: Stévigny Caroline , Jiwan Jean‐Louis Habib , Rozenberg Raoul , de Hoffmann Edmond , Quetin‐Leclercq Joëlle 
Published: February 2004

AbstractThis work reports a detailed study of the fragmentations of aporphine alkaloids by electrospray ionization with multistage mass spectrometry (ESI‐MSn) in positive mode. In a first step the loss of the amino group and its substituent is observed. Further steps display the loss of the peripheral groups. Losses of methanol and CO are observed if an OH is vicinal to an OCH3 on the aromatic ring. Otherwise the spectra show radical losses of CH3. or CH3O. as the main fragmentations. If a methylenedioxy group is present losses of formaldehyde followed by CO are observed. These fragmentations yield important information on the structures of aporphines. Copyright © 2004 John Wiley & Sons, Ltd.
Screening method for pesticides in air by gas chromatography/tandem mass spectrometry
Authors: Egea Gonzalez F. J. , Mena Granero A. , Glass C. R. , Garrido Frenich A. , Martinez Vidal J. L. 
Published: February 2004

AbstractA multiresidue method for determining more than 70 pesticides in air has been validated using a single injection with gas chromatography/tandem mass spectrometry (GC/MS/MS). The method validation considered both stages of sampling and analysis. The sampling method, based on active sampling using sorption in sorbent cartidges, was validated by generating standard atmospheres. Performance parameters of the method were evaluated, with a reduction in the limits of quantification by injecting a higher volume of sample extract, and increase of selectivity by the use of MS/MS detection mode. The method was based on solid‐phase extraction, which permits a degree of automation. The best adsorbents were found to be Chromosorb 106 and Tenax TA. The retention capacity of these sampling sorbents allows up to 1440 L of air to be sampled without any breakthrough for most of the compounds. Data were generated for assessing the potential exposure of bystanders. The application of the method to the analysis of the air in urban locations near agricultural areas showed that pesticides were present in most of the samples. Copyright © 2004 John Wiley & Sons, Ltd.
Negative ion mass spectra of Cys‐containing peptides. The characteristic Cys γ backbone cleavage: a joint experimental and theoretical study
Authors: Bilusich Daniel , Brinkworth Craig S. , Bowie John H. 
Published: February 2004

AbstractThe Cys residue initiates characteristic backbone cleavages of [M−H]− anions of Cys‐containing peptides. A combination of experiment and theory suggests that these processes are initiated by molecular recognition between the C‐terminal CONH− group (in this study all peptides have C‐terminal CONH2 groups) and the SH in the Cys side chain to form an SH ··· OC hydrogen bond. This process is exothermic by 60 kJ mol−1 (calculations at the HF/6‐31G(d)//AM1 level of theory). The structure of this reactive intermediate has the NH− of the amide group and the central CH of the Cys residue locked into position such that these groups effect an SN2 process to form an intermediate which can either (i) dissociate to give an RNH− species [the δ ion (process endothermic by 37 kJ mol−1 with a barrier of 132 kJ mol−1)], or (ii) effect deprotonation within the intermediate to eliminate RNH2 to give the γ backbone cleavage anion in a reaction exothermic by 40 kJ mol−1 with a barrier of 132 kJ mol−1. Collision‐induced mass spectra of the [MH]− anions of five selected Cys‐containing peptides all contain γ and (γ‐H2S) anions. Three of these spectra also show the less favoured δ cleavage anions. Copyright © 2004 John Wiley & Sons, Ltd.
Characterisation of new pyridazinofurocoumarins by electron ionisation and multiple stage tandem mass spectrometry using an ion trap mass spectrometer
Authors: Begala Michela , González‐Gómez Jose Carlos , Podda Gianni , Santana Lourdes , Tocco Graziella , Uriarte Eugenio 
Published: February 2004

AbstractThe inverse electron‐demand Diels‐Alder reaction between furocoumarinones and 3,6‐bis(methoxycarbonyl)‐1,2,4,5‐tetrazine was used to give pyridazinofurocoumarins in good yields. The structural characterisation of the synthesised compounds was achieved by NMR spectroscopy. The mass spectrometric behaviour was studied under electron ionisation conditions via sequential product ion fragmentation experiments (MSn). This study allowed the evaluation of the role played by the methyl substituent on the benzene ring of pyridazinofurocoumarins in their fragmentation pathways. Copyright © 2004 John Wiley & Sons, Ltd.
Evaluation of three ionisation modes for the analysis of chlorinated paraffins by gas chromatography/ion‐trap mass spectrometry
Authors: Castells P. , Santos F. J. , Galceran M. T. 
Published: February 2004

AbstractThe applicability of three ionisation modes to the analysis of short‐chain chlorinated paraffins (SCCPs) using gas chromatography coupled with mass spectrometry (GC/MS) was evaluated. MS conditions for electron ionisation (EI), positive chemical ionisation (PCI) and electron‐capture negative ionisation (ECNI) were optimised using commercially available individual tetra‐, penta‐ and hexachlorodecanes. In addition, mass spectra were studied and fragmentation pathways were proposed for each individual congener. Different fragment ions were evaluated for quantification, and ECNI‐MS using [HCl2]− and [Cl2]−. ions was selected for the determination of SCCPs. Quality parameters (repeatability, limits of detection and calibration range) were established for the proposed method, which was then applied to the analysis of SCCPs in river sediments. Copyright © 2004 John Wiley & Sons, Ltd.
Gas chromatography/mass spectrometric identification of dopaminergic metabolites in striata of rats treated with L‐DOPA
Authors: Loutelier‐Bourhis C. , Legros H. , Bonnet J.‐J. , Costentin J. , Lange C. M. 
Published: February 2004

AbstractThe ex vivo identification of dopaminergic metabolites present in rat striata after (L‐DOPA + benserazide) treatment is reported. The different metabolites have been identified as the trimethylsilyl derivatives in the striatal extracts by gas chromatography/mass spectrometry. Copyright © 2004 John Wiley & Sons, Ltd.
Qualitative analysis of phenolic compounds in apple pomace using liquid chromatography coupled to mass spectrometry in tandem mode
Authors: Sánchez‐Rabaneda Ferran , Jáuregui Olga , Lamuela‐Raventós Rosa Maria , Viladomat Francesc , Bastida Jaume , Codina Carles 
Published: February 2004

AbstractThe occurrence of phenolic compounds in apple residues resulting from the juice industry was investigated to provide an alternative use for this raw material. For the identification of these compounds, liquid chromatography coupled to ionspray mass spectrometry in tandem mode (LC/MS/MS) with negative ion detection was used. The residues were first extracted and then chromatographed on Sephadex LH‐20 to yield 13 fractions. Positive identification of the compounds was based on their retention times and mass spectra in full scan mode (MS), and in different MS/MS modes (product ion scan, precursor ion scan and neutral loss scan). In this way, 60 compounds, including cinnamic and benzoic acid derivatives and flavonoids, were identified, some of them not previously reported in apple waste. Copyright © 2004 John Wiley & Sons, Ltd.
Quantitative measurement of different ceramide species from crude cellular extracts by normal‐phase high‐performance liquid chromatography coupled to atmospheric pressure ionization mass spectrometry
Authors: Pettus Benjamin J. , Kroesen Bart‐Jan , Szulc Zdizslaw M. , Bielawska Alicia , Bielawski Jacek , Hannun Yusuf A. , Busman Mark 
Published: February 2004

AbstractNormal‐phase high‐performance liquid chromatography (NP‐HPLC) coupled to atmospheric pressure ionization mass spectrometry (APCI‐MS) allows quantitative analysis of endogenous ceramide and dihydroceramide species from crude lipid extracts. Qualitative information for the species comes from observation of differences in chromatographic and mass spectrometric behavior between species (Pettus et al. Rapid Commun. Mass Spectrom. 2003; 17: 1017–1026). Quantitative analysis is achieved by (1) use of a synthetic internal standard as an extraction and injection control, (2) lack of salt adduction, ion suppression, or other matrix effects in APCI mode, and (3) consistent fragmentation and ionization of external standards across the physiologically relevant concentration range found in endogenous lipid samples. Application to the analysis and quantitation of ceramide and dihydroceramide from various cell lines is demonstrated. The results from APCI‐MS analysis corroborate and enhance information acquired from use of the diacylglycerol kinase assay for total ceramide measurement. This technique readily allows simultaneous quantitation of ceramide and dihydroceramide species. Copyright © 2004 John Wiley & Sons, Ltd.
m‐ary Search trees when m ≥ 27: A strong asymptotics for the space requirements
Authors: Chauvin Brigitte , Pouyanne Nicolas 
Published: February 2004

AbstractIt is known that the joint distribution of the number of nodes of each type of an m‐ary search tree is asymptotically multivariate normal when m ≤ 26. When m ≥ 27, we show the following strong asymptotics of the random vector Xn = t(X, … , X), where X denotes the number of nodes containing i − 1 keys after having introduced n − 1 keys in the tree: There exist (nonrandom) vectors X, C, and S and random variables ρ and φ such that (Xn − nX)/n − ρ(C cos(τ2log n + φ) + S sin(τ2log n + φ)) →n→∞ 0 almost surely and in L2; σ2 and τ2 denote the real and imaginary parts of one of the eigenvalues of the transition matrix, having the second greatest real part. © 2004 Wiley Periodicals, Inc. Random Struct. Alg., 2004
Functions that have read‐twice constant width branching programs are not necessarily testable
Authors: Fischer Eldar , Newman Ilan , Sgall Jiří 
Published: February 2004

AbstractWe construct a property on 0/1‐strings that has a representation by a collection of width‐3 read‐twice oblivious branching programs, but for which any two‐sided ϵ‐testing algorithm must query at least Ω(nδ) many queries for some fixed ϵ and δ. This shows that Newman's result [Testing of functions that have small width branching programs, SIAM J Comput 31 (2002), 1557–1570] cannot be generalized to read‐k‐times functions fork> 1. In addition, we exhibit a property that has also a representation by a CNF formula of constant clause size. Hence, the nontestability results extend to properties that in addition have small (constant size) 0‐witnesses. © 2004 Wiley Periodicals, Inc. Random Struct. Alg., 2004
The rotation correspondence is asymptotically a dilatation
Authors: Marckert Jean‐François 
Published: February 2004

AbstractThe rotation correspondence is a map that sends the set of plane trees onto the set of binary trees. In this paper, we first show that when n goes to +∞, the image by the rotation correspondence of a uniformly chosen random plane tree τ with n nodes is close to 2τ (in a sense to be defined). The second part of the paper is devoted to the right and left depth of nodes in binary trees. We show that the empiric measure (suitably normalized) associated with the difference of the right depth and the left depth processes converges to the integrated super Brownian excursion. © 2004 Wiley Periodicals, Inc. Random Struct. Alg., 2004
Adding random edges to dense graphs
Authors: Bohman Tom , Frieze Alan , Krivelevich Michael , Martin Ryan 
Published: February 2004

AbstractThis paper investigates the addition of random edges to arbitrary dense graphs; in particular, we determine the number of random edges required to ensure various monotone properties including the appearance of a fixed size clique, small diameter and k‐connectivity. © 2004 Wiley Periodicals, Inc. Random Struct. Alg., 2004
Divide and conquer martingales and the number of triangles in a random graph
Authors: Kim J. H. , Vu V. H. 
Published: February 2004

AbstractThe goal of this paper is to present a novel application of a recent and useful martingale inequality. As an illustration, we prove an essentially sharp bound for the probability that a random graph contains significantly more triangles than expected. © 2004 Wiley Periodicals, Inc. Random Struct. Alg., 2004
Counting the onion
Authors: Dalal Ketan 
Published: February 2004

AbstractIteratively computing and discarding a set of convex hulls creates a structure known as an “onion.” In this paper, we show that the expected number of layers of a convex hull onion for n uniformly and independently distributed points in a disk is Θ(n2/3). Additionally, we show that in general the bound is Θ(n2/(d+1)) for points distributed in a d‐dimensional ball. Further, we show that this bound holds more generally for any fixed, bounded, full‐dimensional shape with a nonempty interior. © 2004 Wiley Periodicals, Inc. Random Struct. Alg., 2004
K5‐free subgraphs of random graphs
Authors: Gerke S. , Schickinger T. , Steger A. 
Published: February 2004

AbstractWe consider a conjecture by Kohayakawa, Łuczak, and Rödl, which, if true, would allow the application of Szemerédi's regularity lemma to show Turán‐type results for all random graphs and any fixed graph H. We deal with 5‐partite graphs such that each part contains n vertices, and any two parts form an ε‐regular pair with m edges. Here, two sets of vertices U and W of size n form an ε‐regular pair with m edges if all subsets U′ ⊆ U and W′ ⊆ W with |U′|, |W′| ≥ εn satisfy ||E(U′, W′)| − |U′| |W′|m/n2| ≤ ε|U′| |W′|m/n2. We show that for each β > 0, there exists at most βm()10 such graphs that do not contain a K5 as a subgraph if m ≥ Cn5/3 for a constant C = C(β), ε is sufficiently small, and n is sufficiently large. This proves the special case of the conjecture when H equals the complete graph on five vertices. © 2004 Wiley Periodicals, Inc. Random Struct. Alg., 2004
Extraction and quantitative analysis of aneurysmal aorta for aiding endovascular stent grafting
Authors: Imamura Hiroshi , Sugimoto Naozo , Eiho Shigeru , Urayama Shin‐ichi , Ueno Katsuya , Inoue Kanji 
Published: February 2004

AbstractIn performing interventions including stent grafting, the suitability for stent grafting must be checked and the devices to be used must be designed preoperatively. For these purposes, the three‐dimensional shapes of the blood vessels in lesions or the paths of device placement must be measured accurately and quickly. In this paper, a method for measuring the aortal shape from CT angiogram (CTA) and for detecting lesions from the shape characteristics of these is presented. Specifically, this method extracts the blood flow area of the aorta by using a three‐dimensional edge‐preserving smoothing filter and a region growing method. Extracted blood vessels are classified by using their anatomical characteristics. After initial setting of the medial axis in a blood vessel, it determines the aneurysmal area based on the diameter of the blood vessel and modifies the medial axis. In addition, it detects lesions such as thrombi and calcifications near the blood flow borderline. Application of the method to 30 clinical cases has confirmed that the proposed method is effective in obtaining the shape of blood vessels. © 2004 Wiley Periodicals, Inc. Syst Comp Jpn, 35(3): 58–67, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/scj.10223