bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ambient oxygen ingress rate method—an alternative method to Ox‐Tran for measuring oxygen transmission rate of whole packages
Authors: Larsen Hanne , Kohler Achim , Magnus Ellen Merethe 
Published: August 2002

AbstractThe ambient oxygen ingress rate method (AOIR) is an alternative method to Ox‐Tran for measuring the oxygen transmission rates (OTR) of whole packages. The objective of the present work was (a) to compare OTR values obtained by the two methods, and (b) to evaluate the use of the AOIR method for measuring OTR at realistic food storage temperatures and humidity levels. The AOIR method gave equal OTR values compared to the Ox‐Tran method for the five different types of whole packages used in the experiment, with OTR values in the range 0.06–1.48 ml O2/day. The repeatability of the AOIR method measured on an HDPE bottle was ±2.6% of the measured value in this experiment. This is slightly higher than the general specifications of the Ox‐Tran method (1% of reading for packages). However, the AOIR method can be considered to be a reliable, precise and cheap alternative method to the Ox‐Tran method for measuring OTR of whole packages. The capacity of the method is also high. The AOIR method showed satisfactory results when comparing OTR for packages tested under realistic food storage conditions covering 23°C/50% relative humidity (RH) and at 4°C/60% RH on the outside, combined with water (100% RH) or dry air inside the packages. Copyright © 2000 John Wiley & Sons, Ltd.
Process capability analysis in the presence of autocorrelation
Authors: Noorossana R. 
Published: August 2002

AbstractProcess capability analysis when observations are autocorrelated is addressed using time series modelling and regression analysis. Through the use of a numerical example, it is shown that the variance estimate obtained from the original data is no longer an appropriate estimate to be considered for conducting process capability analyses. Copyright © 2002 John Wiley & Sons, Ltd.
Simple method for the precise calculation of atomic energy levels of IB elements in the periodic table
Authors: Zheng Nengwu , Wang Tao , Ma Dongxia , Zhou Tao 
Published: August 2002

AbstractDue to the complicated and typical electronic structure of atoms and ions of the IB group in the periodic table, theoretical calculation of their atomic energy levels has important theoretical and practical significance. In this article, the theoretical calculation of atomic energy levels of the atoms of IB group in the periodic table was completed for the first time within the scheme of the weakest bound electron potential model theory. The results were compared with experimental values and the deviations are about 0.1–1 cm−1. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Categorization of visualization tools in aspects of chemical research and education
Authors: Burewicz Andrzej , Miranowicz Nikodem 
Published: August 2002

AbstractChemistry is an experimental science whose research subjects are often not directly available within the close dimensions of a time or space. To optimize a particular teaching process or research, it is necessary to visualize phenomena, processes, or objects. Consequently, visualization is significant to problem solving in research and teaching. Visualization is applicable in those situations when it is required to reduce the dimensions of experimental objects to given numbers and values accessible to direct experience. In educational practice, this is related to one of the following situations: (1) the experiment is too long or too short; (2) the dimensions of the examined object are too small or too large; (3) the environment of the experiment is not accessible; (4) the parameters of the experiment or its effects are not directly available to the observer's senses; (5) there is a need for multiple revisions of the experiment; (6) the experiment is difficult to arrange or revise effectively; (7) the experiment is dangerous; (8) the experiment is too expensive; etc. The presentation of models of physicochemical processes and phenomena, models of atoms and molecules, and mechanisms of reaction, as well as experimental data and their mathematical models, provides a basis for considering the formulation of correct conclusions. The appropriate choice of visualization algorithms is decisive of the effectiveness of theoretical analyses. The main aspect of visualization is obviously its application to teaching or research. Thus, the choice of techniques depends on whether it is used for recognition, explanation, memorization, inspiration, or motivation. In research, the importance as well as area of usefulness of three main categories of visualization have also been established. These categories are: illustration—relating to the presentation of an existing picture of object; representation—the presentation of an image assigned to an object; and visualization—related to the presentation of an image created for the object. Research work on preparing means for visualization confirms that, depending on the particular aspect of categorizing visualization, it may be useful, as well, to assign additional criteria such as dimensions, degree, functions, methodological contexts, experimental relationship, and medial effectiveness into visualization. In recent years, at the Institute of Chemical Education of Poznan's Adam Mickiewicz University such research was undertaken. Its main aim was to determine the educational effectiveness of different types of chemical visualizations. Methods for the visualization of chemical issues were developed and a series of original video and animation sequences presenting different aspects of chemical visualization prepared. Interactive Internet instructions sets were produced and methods of visualization categorized. Effectiveness in using different types of chemical visualizations was estimated. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
Deduction of the Klein–Fock–Gordon equation from a non‐Markovian stochastic equation for real pure‐jump process
Authors: Skorobogatov G. A. 
Published: August 2002

AbstractFrom the Madelung's work in 1926, it became clear that the pair of adjoint Schrödinger equations is equivalent to two equations of hydrodynamic representation for probability density and mean momentum Both these equations can be derived from the quantum transport equation (QTE) for a probability density P(, , t) as two equations for the two first moments Then, QTE can be obtained from a non‐Markovian stochastic Kolmogorov–Gikhman–Skorokhod equation for a real pure‐jump process. Similarly, the Klein–Fock–Gordon equation follows from non‐Markovian relativistic QTE (RQTE). Thus, all quantum mechanics as mathematical theory is a topic of the theory of real pure‐jump non‐Markovian stochastic processes. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002
A note on nodal structures, partial screening, and periodic trends among alkali metals and alkaline earths
Authors: Pyykkö Pekka 
Published: August 2002

AbstractThe first ionization potential of Na is close to that of Li but much larger than that of K. Similar trends were noted for the electronegativities or for the calculated atomic charges in partially covalent alkali metal hydrides MH or methide compounds, MCH3 (M=Li–Cs) by Lambert, Kaupp, and Schleyer. This trend can be understood by combining the effects of the nodal structure, as function of the principal quantum number, n, and the lanthanide contraction‐like effects of partial screening from both the 1s and 2p shells. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Symplectic molecular dynamics integration using normal mode analysis
Authors: Janežič Dušanka , Praprotnik Matej 
Published: August 2002

AbstractThe split integration symplectic method (SISM) for molecular dynamics (MD) integration using normal mode analysis based on a factorization of the Liouville propagator is presented. This approach is quite distinct from others that use fractional‐step methods, owing to the analytical treatment of high‐frequency motions. The method involves splitting the total Hamiltonian of the system into a harmonic part and the remaining part. Then the Hamilton equations are solved using a second‐order generalized leapfrog integration scheme in which the purely harmonic Hamiltonian (which represents the main contribution of the chemical bonds and angles) is treated analytically, i.e., independent of the step size of integration, by a normal mode analysis that is carried out only once, at the beginning of calculation. The whole integration step combines analytical evolution of the harmonic part of the Hamiltonian with a correction arising from the remaining part. The proposed algorithm requires only one force evaluation per integration step. The algorithm was tested on a simple system of linear chain molecules. Results demonstrate the method makes possible the integration of the MD equations over larger time steps without loss of stability while being economical in computer time. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 84: 2–12, 2001
Semiempirical and spectroscopic study of a novel porphyrin dyad
Authors: Janvier P. , Le Questel J.‐Y. , Illien B. , Suresh S. , Blart E. , Quintard J.‐P. , Odobel F. 
Published: August 2002

AbstractSemiempirical calculations and ultraviolet–visible experiments have been carried out on a novel bisporphyrin system. The present work reveals that an oligothiophene ethynyl‐linked spacer promotes high electronic interactions over a large distance in this dyad. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem 84: 259–263, 2001
Theoretical study of the vertical electron excitation of linear carbon clusters C3, C5, and C7
Authors: Giuffreda M. G. , Deleuze M. S. , François J.‐P. , Trofimov A. B. 
Published: August 2002

AbstractThe vertical electron excitation spectra of linear carbon clusters C3, C5, and C7 have been investigated by means of polarization propagator calculations using the second‐order algebraic diagrammatic construction [ADC(2)] scheme. The structure of singlet and triplet excited‐state manifolds below the lowest ionization threshold has been analyzed in detail for the smallest prototype cluster C3. The electronic spectra of all three molecules contain numerous low‐lying single and double valence excitations, reflecting strongly the correlated nature in these clusters. The density of the excited states becomes increasingly high above the onset of Rydberg excitations. A substantial mixing of various valence and Rydberg configurations in this region does not allow for simple interpretation of the final electronic states. The spectroscopic and photophysical implications of this complex situation are discussed. Where possible the computed excitation energies and oscillator strength are compared with available experimental and previous theoretical data. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001
Structural determination of lysophosphatidylcholines extracted from marine sponges by fast atom bombardment tandem mass spectrometry
Authors: Hong Jongki , Cho Kun , Kim Young Hwan , Cheong Chaejoon , Lee Kwang‐Sik , Jung Jee H. 
Published: August 2002

AbstractA series of lysophosphatidylcholines were isolated from the marine sponge Spirastrella abata by reversed‐phase high performance liquid chromatography (HPLC) and analyzed by fast atom bombardment mass spectrometry (FAB‐MS). Their structural elucidation was carried out with fast atom bombardment tandem mass spectrometry (FAB‐MS/MS). The collision‐induced dissociation (CID) of protonated and sodiated molecular ions produced diverse product ions via a series of dissociative processes. Because of the positive charge of the amine group at the end of the molecules, charge‐remote fragmentation patterns of specific ions, [M + H]+ or [M + Na]+, were very helpful for the identification of product ions which are characteristic for choline and long hydrocarbon chains substituted at the glycerol back bone. Moreover, the CID‐MS/MS spectra of sodium adducted molecular ions for lysophosphatidylcholines yielded common characteristic fragment ions for the choline moiety and characteristic ions [M + Na‐103]+, [M + Na‐85]+ and [M + Na‐59]+ in the higher mass region. Copyright © 2001 John Wiley & Sons, Ltd.
Two‐photon ionization thresholds of matrix‐assisted laser desorption/ionization matrix clusters
Authors: Lin Qiong , Knochenmuss Richard 
Published: August 2002

AbstractDirect two‐photon ionization of the matrix has been considered a likely primary ionization mechanism in matrix‐assisted laser desorption/ionization (MALDI) mass spectrometry. This mechanism requires that the vertical ionization threshold of matrix materials be below twice the laser photon energy. Because dimers and larger aggregates may be numerous in the early stages of the MALDI plume expansion, their ionization thresholds are important as well. We have used two‐color two‐photon ionization to determine the ionization thresholds of jet cooled clusters of an important matrix, 2,5‐dihydroxy benzoic acid (DHB), and mixed clusters with the thermal decomposition product of DHB, hydroquinone. The thresholds of the clusters were reduced by only a few tenths of an eV compared to the monomers, to an apparent limit of 7.82 eV for pure DHB clusters. None of the investigated clusters can be directly ionized by two nitrogen laser photons (7.36 eV), and the ionization efficiency at the thresholds is low. Copyright © 2001 John Wiley & Sons, Ltd.
Loss of charged versus neutral heme from gaseous holomyoglobin ions
Authors: Chrisman Paul A. , Newton Kelly A. , Reid Gavin E. , Wells J. Mitchell , McLuckey Scott A. 
Published: August 2002

AbstractThe dissociation of holomyoglobin ions ranging in charge state from +10 to +2 has been studied using collisional activation in a quadrupole ion trap. Collisional activation times and amplitudes were varied to investigate the effects of these variables on dissociation of the heme group from the holoprotein. The onset of neutral heme loss occurs at a lower activation amplitude than loss of charged heme. For solutions of ferri‐myoglobin, charged heme loss was prominent for +10 to +4 holomyoglobin ions, while neutral heme loss product was found to be dominant for charge states +3 and +2. For any given charge state, activation of holomyoglobin ions from a solution containing primarily ferro‐myoglobin yielded significantly more abundant neutral heme loss products than was observed for activation of ions from solutions containing primarily ferri‐myoglobin. The relative concentrations of the two oxidation states were shown to be affected by redox chemistry within the nano‐electrospray emitter used in this work. Results from a double activation experiment revealed that the precursor ions of a given charge state contained a mixture of two populations, with ferro‐myoglobin giving rise to neutral heme loss upon dissociation and ferri‐myoglobin yielding charged heme. No evidence for electron transfer upon collisional activation of ferri‐myoglobin ions was observed. Furthermore, little or no evidence for electron transfer associated with ion/ion reactions with anions derived from perfluoro‐1,3‐dimethylcyclohexane was observed. Definitive results could not be drawn for the lowest precursor ion charge states (+3 and +2) due to low dissociation efficiencies. Copyright © 2001 John Wiley & Sons, Ltd.
Two‐dimensional separations with electrospray ionization ambient pressure high‐resolution ion mobility spectrometry/quadrupole mass spectrometry
Authors: Matz Laura M. , Asbury G. Reid , Hill Herbert H. 
Published: August 2002

AbstractThe coupling of ion mobility spectrometry (IMS) instruments with mass spectrometers has been described since early in IMS development, most commonly with quadrupole mass analyzers. The recent development of IMS with time‐of‐flight (TOF) instruments has demonstrated that the time compatibility (IMS milliseconds and TOFMS microseconds) of the two techniques enables rapid two‐dimensional separations to be performed, theoretically in the order of seconds for a complete analysis. This study presents a unique way to operate a traditional IMS/QMS system to attain separations similar to those achieved with IMS/TOF. For this new approach, the quadrupole was slowly scanned in the single‐ion monitoring mode while IMS spectra were continually embedded in each m/z step. In this way, two‐dimensional separations (IMS drift times and m/z) were obtained using the traditional IMS/QMS arrangement. An example of a five amino acid separation (quadrupole scan of 40 m/z values at a rate of ∼7 steps/min) led to a complete two‐dimensional analysis within 6 min, comparable to rapid chromatographic separations with mass spectrometry. Proposed approaches to reduce the analysis time are discussed and a reduction in the analysis time to less than 1 min is feasible when the IMS/QMS separation conditions are optimized. Copyright © 2002 John Wiley & Sons, Ltd.
Time‐of‐flight studies of secondary ions produced by 400 eV He+ ion impact on Ar, Kr, and Xe thin films at 8 K
Authors: Hiraoka Kenzo , Watanabe Makoto , Eguchi Daisuke , Okazaki Shigemitsu , Sato Tetsuya 
Published: August 2002

AbstractSecondary ions produced by 400 eV He+ ion impact on Ar, Kr, and Xe thin films deposited on a silicon substrate at 8 K were measured as a function of film thickness using a time‐of‐flight secondary‐ion mass spectrometer. For Ar, the cluster ions Arn+ up to n = 4 as well as the monomer ion (n = 1) were observed and they showed characteristic film‐thickness dependence with increase of the film thickness up to ∼200 monolayers. This is due to the momentum transfer in the elastic collision between the incident He+ ion and the matrix Ar atoms and also to the relaxation of electronic excitations (e.g., holes and excitons) to phonons resulting in the film erosion. In contrast, neither dimer nor cluster ions were detected for solid Kr and Xe films. This is due to the less efficient momentum transfer in the elastic collision between He+ and Rg's (Rg = Kr and Xe) and also to the efficient electronic energy migration in solid Kr and Xe. The ions originating from the silicon substrate such as Si+, SiCH3+, SiOH+, and C+ were found to be sensitized by the deposition of Xe film in the range of 0–40 monolayers. The penetration depths of the primary ion He+ through the rare gas films increase in the order Ar < Kr < Xe. Copyright © 2002 John Wiley & Sons, Ltd.
Considerations for design of a Fourier transform mass spectrometer in the 4.2 K cold bore of a superconducting magnet
Authors: O'Connor Peter B. 
Published: August 2002

AbstractAn external source Fourier transform mass spectrometer (FTMS) constructed inside the vertical cold bore of a superconducting magnet will have dramatic advantages in effective magnetic field, noise figures, and base pressure over current commercially available external source FTMS systems. There are substantial, but solvable, difficulties in the design, primarily with regard to control of the helium boiloff rate to an acceptable level, as well as relatively minor design challenges with heat sinks, contraction of metallic ion optic elements in the extreme temperature, and tandem mass spectrometry experiments. However, the ability to construct the FTMS inside the narrow bore tube of existing, commercially available vertical bore NMR magnets will allow access to the upper magnetic field limit currently used by 900 MHz (21 Tesla) – 1 GHz (23.3 Tesla) NMR experiments. The vacuum system, simply by being held inside the cold bore at 4.2 K, will cryopump itself dropping base pressures substantially, and heat sinking the input resistor of the preamplifier to this cryogenically cooled vacuum chamber will allow reduction of the input Johnson noise by a factor of 8.4 with associated 8.4‐fold improvement in signal/noise, sensitivity, and dynamic range. The simultaneous improvement of three fundamental limiting factors in the FTMS (field strength, base pressure, and Johnson noise figure) will clearly outweigh the concomitant increased helium boiloff rate particularly if this rate can be dropped to the estimated <5 L/day range. The additional use of modern cryorefrigerators will further reduce helium boiloff to zero except during MSn experiments and system cooldown. Copyright © 2002 John Wiley & Sons, Ltd.
Nordic consumers and the challenge for sustainable housing
Authors: Svane Örjan 
Published: August 2002

AbstractIn the Nordic countries, housing is one of society's greatest users of resources. Making housing more sustainable will call for changes in buildings, management routines and residents' habits, each having its possibilities as well as a built in resistance against change. Households might play a key role in this change, directly as consumers, but also indirectly and jointly as pressure groups towards real estate owners, managers and local society. Making housing more sustainable can be seen as society's ‘sustainability challenge’ to the housing consumers. In this paper, the extent of this challenge is discussed for the households of the Nordic countries, for different types of ownership and building etc. Its realization is seen in a ten‐year perspective and in relation to the acquisition, maintenance, operation and use of the dwellings. Preliminary results indicate that a move to a new dwelling will give the household an opportunity to influence many aspects of its environmental impacts, but that moving will have little direct effect on the environmental performance of the built environment as a whole. Furthermore, that the activities of daily living have a potential for improvement without the inertia of reconstructing the building stock. In the end, however, co‐operation between households and other stakeholders of the building sector is often a prerequisite for change. Copyright © 2002 John Wiley & Sons, Ltd. and ERP Environment.
Characterization of finishing on polyamide fibres
Authors: Biganska Olga , Darque‐Ceretti Evelyne , Giulieri Françoise , Combarieu Robert 
Published: August 2002

AbstractFor a fundamental approach to fibres for composite applications, it is essential to develop efficient methods to analyse the composition and distribution of the sizing layer on the fibres. The aim of this investigation is to propose a combination of methods for surface characterization of manufactured finished fibres. The task is not straightforward because the composition of finishing is usually kept secret. Polyamide fibres with two different types of finishing are investigated by mean of several methods: optical microscopy and scanning electron microscopy (SEM), x‐ray photoelectron spectroscopy (XPS), time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) and Langmuir balance for monolayer study. Classical methods of observation and analysis (microscopy, XPS and ToF‐SIMS) applied directly to the fibres do not show any difference in the two types of finishing. Only the Langmuir balance demonstrates the difference between two types of fibres finishing. At the water contact, only one of the two types of fibres loses a compressible monolayer of insoluble substance on the water surface. This layer then is characterized by ToF‐SIMS. An attempt to describe the finishing composition is made. Copyright © 2001 John Wiley & Sons, Ltd.