bluuebunny/crossref_metadata_2025_split huggingface dataset:
Magnetic properties of a transverse spin‐$ {3 \over 2} $ Ising model with random longitudinal field
Authors: Liang Ya‐Qiu , Wei Guo‐Zhu , Song Guo‐Li 
Published: November 2004

AbstractWithin the framework of the effective‐field theory with correlations, a spin‐$ {3 \over 2} $ transverse Ising model in the longitudinal random‐field on a honeycomb lattice is studied. The phase diagrams and the behavior of the tricritical point are examined. The possible re‐entrance phenomena displayed by the system due to the competition effects that occur for the appropriate ranges of the random and transverse field are investigated. The longitudinal and transverse magnetizations, the longitudinal quadrupolar moments and internal energy are given numerically for a honeycomb lattice (z = 3). (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Improvement of photoluminescence efficiency in stacked Ge/Si/Ge quantum dots with a thin Si spacer
Authors: Chen P. S. , Lee S. W. , Peng Y. H. , Liu C. W. , Tsai M.‐J. 
Published: November 2004

AbstractIn this work, two successive layers of Ge quantum dots separated by a thin Si spacer grown by ultra‐high‐vacuum chemical vapor deposition were demonstrated. With an optimal thickness of the thin Si spacer, the sandwiched Ge (13.1 ML)/Si (28 ML)/Ge (13.1 ML) quantum dots suppress the coarsening of Ge quantum dots and efficiently increase the uniformity of the quantum dots. Cross‐sectional transmission electron microscopy shows that the Si/Ge underlayers provide preferred nucleation sites for the overlayer Ge deposition. Such a modification avoids the formation of Ge superdomes and prevents the occurrence of threading dislocations even at such a thin Si spacer thickness. A stronger photoluminescence intensity of these sandwich Ge/Si/Ge quantum dots was observed compared with that of 26.2 eq‐ML Ge quantum dots without using any intermediate Si layer. Furthermore, the narrower width of the photoluminescence spectra indicates that the Ge/Si/Ge dots are more uniform compared with the 13.1 and 26.1 eq‐ML Ge quantum dots. Five‐fold bilayers of Ge/Si/Ge/Si(150 ML) have been achieved to enhance the photo‐emission efficiency. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigations on the local structures of the two trigonal Er3+ centers in KMgF3
Authors: Wu Shao‐Yi , Dong Hui‐Ning , Wei Wang‐He 
Published: November 2004

AbstractThe local structures of the two trigonal Er3+ (167Er) centers I and II in KMgF3 are theoretically studied using the perturbation formulas of the g factors for a 4f11 ion in trigonal symmetry. In these formulas the contributions to the g factors from the second‐order perturbation terms and admixtures of various states are taken into account. Based on the studies, the centers I and II are attributed to, respectively, the Er3+ impurity occupying the octahedral Mg2+ site with a K+ vacancy VK and the dodecahedral K+ site with a Mg2+ vacancy VMg along the C3 axis due to charge compensation. According to the calculations, the Er3+ ion in either center is found to undergo an axial displacement ΔZL (L = I or II) towards the compensator (VK or VMg) along the C3 axis because of electrostatic attraction. The calculated g factors for both the Er3+ centers based on the displacements ΔZL show reasonable agreement with the observed values. The local structures of the two centers are discussed. The theoretical studies in this paper may be useful for understanding the optical properties of Er3+‐doped KMgF3. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetoconductivity of planar crystalline systems and its semiclassical quantization
Authors: Olszewski S. , Pietrachowicz M. , Baszczak M. 
Published: November 2004

AbstractThe tensor of magnetoconductivity is examined for the tightly‐bounds‐electrons in the planar crystallographic lattices originating from three cubic lattice kinds (simple, body‐centered and face‐centered). The magnetic field is assumed to be directed perpendicularly to the crystallographic plane and the relaxation time entering the conductivity tensor is derived from the crystal band structure. The presence of the lattice potential is found to be essential for calculating a finite value of the Hall conductivity, which, in general, exhibits a rather feeble dependence on position of the Landau level within the energy band. A quasi‐constant behavior in the band of states is obtained also for a quantal increment of the Hall conductivity between two neighboring Landau levels. For different cubic lattices this increment is an approximately constant number being close toe2/h. On the other hand, the quanta of the diagonal components of the tensor of magnetoconductivity per one Landau level are much larger thane2/hfor an almost empty band, but they tend to decrease very rapidly to zero with an increase of the band filling. For a strong magnetic field – and not too low temperatures – the components of the tensor of magnetoresistance are found to increase linearly with the strength of the field. A remarkable quantitative agreement between the theory and experiment is demonstrated for the Hall resistance of the planar crystalline structures. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Binding energy of relativistic hydrogenic impurities in cylindrical quantum well wires under an applied electric field
Authors: Meşe A. I. , Okan S. E. 
Published: November 2004

AbstractThe ground state binding energy of a hydrogenic impurity in infinite cylindrical GaAs quantum well wires subjected to an external electric field applied perpendicular to the symmetry axis of the wire is studied within the relativistic approach. A rapid decrease of the binding energy for different intensities of the electric field with increasing wire radius is predicted. Furthermore, the relativistic effects are emphasised by comparing them with the non‐relativistic results. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Low‐field magnetic behavior of LaMn2–xNixSi2 silicides
Authors: Gencer A. , Kįlįç A. , Kervan S. 
Published: November 2004

AbstractWe have performed X‐ray diffraction (XRD) and AC magnetic susceptibility measurements on polycrystalline LaMn2–xNixSi2 (0.0 ≤ x ≤ 2.0) silicides for magnetic characterization in fields of about a few Oe at a temperature range 15–325 K. All compounds crystallize in the naturally layered ThCr2Si2‐type structure with the space group I4/mmm. Substitution of Ni for Mn leads to a linear decrease in the lattice constant c and the unit cell volume, while it gives rise to a change of magnetic properties from ferromagnetic to anti‐ferromagnetic behavior for small values of x < 1. The sample with x = 0.8 has a Néel temperature of about 35 K, associated with anti‐ferromagnetic behavior. However, for x = 1, anti‐ferromagnetic behavior is diminished and paramagnetic behavior becomes dominant. For x = 2, the sample becomes virtually non‐magnetic. The samples with x ≤ 0.5 exhibit mixed magnetic properties composed of ferromagnetic and anti‐ferromagnetic interactions, below the Curie temperature TC(Mn). The results are collected in the magnetic phase diagram. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
How do electrons travel in unusual metallic fluorides of Ag2+?
Authors: Jaroń Tomasz , Grochala Wojciech , Hoffmann Roald 
Published: November 2004

AbstractWe investigate computationally two representative examples of higher fluorides of Ag(II), namely KAgF3 and AgFBF4. Both compounds formally contain linear (Ag–F)+ chains, in which divalent silver is coordinated additionally by four fluoride anions. For AgFBF4, the equatorial coordination is weak, and leads to metallic conductivity in 1D, as emerges from our band structure calculations. For KAgF3, however, the axial coordination is very strong, and the compound is virtually a 2D metal (i.e. it is mainly the x2–y2 orbitals of Ag that participate in electronic transport in this interesting material). (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Multi‐residue liquid chromatography/tandem mass spectrometry method for the detection of non‐steroidal anti‐inflammatory drugs in bovine muscle: optimisation of ion trap parameters
Authors: Van Hoof Nathalie , De Wasch Katia , Poelmans Sofie , Noppe Herlinde , De Brabander Hubert 
Published: November 2004

AbstractA multi‐residue liquid chromatography/tandem mass spectrometry method (LC/MS2) was developed for the detection of the non‐steroidal anti‐inflammatory drugs acetylsalicylic acid (via the marker residue salicylic acid), flunixin, phenylbutazone, tolfenamic acid, meloxicam and ketoprofen, in bovine muscle. After extraction of the bovine muscle with acetonitrile, the cleanup was performed using a Oasis HLB column. The evaporated eluate was reconstituted and analysed by LC/MS2. To obtain optimal detection of salicylic acid and phenylbutazone, the ion trap mass spectrometric parameters activation q and maximum ion injection time, respectively, were optimised. The activation q for salicylic acid was increased to obtain reliable detection of both salicylic acid and its product ion. The maximum ion injection time for the time segment containing phenylbutazone was decreased since there were not enough scans across the chromatographic peak of this compound. The multi‐residue method was able to detect the different analytes below or at the maximum residue limit (MRL) or minimum required performance limit (MRPL) or, in the case of phenylbutazone and ketoprofen, at 100 and 20 μg kg−1, respectively. Copyright © 2004 John Wiley & Sons, Ltd.
Use of 18O3‐clodronate as an internal standard for the quantitative analysis of clodronate in human plasma by gas chromatography/electron ionisation mass spectrometry
Authors: Leis Hans Jörg , Fauler Günter , Windischhofer Werner 
Published: November 2004

AbstractA sensitive and specific method for the quantitative determination of clodronate in human plasma is presented. The drug was extracted from plasma by anion‐exchange chromatography and derivatised to the tetra‐tert‐butyldimethylsilyl derivative. 18O3‐Clodronate was prepared from unlabeled clodronate and used as an internal standard. Gas chromatography/mass spectrometry (GC/MS) under electron ionisation conditions was used for quantitative measurement of the drug, using m/z 643.16 and 651.17 for target and internal standard, respectively. Calibration graphs were linear within the range of 10–1280 ng/mL plasma. Intra‐day precision was 1.8% (10 ng/mL), 0.5% (40 ng/mL), 1.0% (120 ng/mL), 0.5% (200 ng/mL), 0.5% (400 ng/mL) and 2.7% (800 ng/mL) and inter‐day variability was found to be 0.7% (10 ng/mL), 1.6% (40 ng/mL), 1.3% (120 ng/mL), 2.3% (200 ng/mL), 2.5% (400 ng/mL) and 1.2% (800 ng/mL). Intra‐day accuracy showed deviations of 0.8% (10 ng/mL), 0.8% (40 ng/mL), 0.9% (120 ng/mL), 0.9% (200 ng/mL), 1.9% (400 ng/mL) and 0.3% (800 ng/mL) and intra‐day accuracy was of −1.4% (10 ng/mL), 0.0% (40 ng/mL), −0.7% (120 ng/mL), −0.4% (200 ng/mL), −1.2% (400 ng/mL) and −3.3% (800 ng/mL). The stable isotope labeled standard was found to be stable under analysis conditions. Copyright © 2004 John Wiley & Sons, Ltd.
Assay of histamine by nano‐liquid chromatography/tandem mass spectrometry with a packed nanoelectrospray emitter
Authors: Song Yaru , Quan Zhe , Liu Yi‐Ming 
Published: November 2004

AbstractA nano‐liquid chromatographic /tandem mass spectrometric (nanoHPLC/MS/MS) method has been developed for the sensitive determination of histamine, a vital neurotransmitter. The method involved pre‐column derivatization of histamine with 7‐fluoro‐4‐nitrobenzoxadiazole (NBD‐F), thus increasing the hydrophobicity of the analyte and allowing it to be retained and stacked on a nanoelectrospay emitter packed with C18 reversed‐phase particles. Sodium 1‐heptanesulfonate, added as an ion‐pairing reagent in the mobile phase for sample loading, was found to facilitate greatly the analyte retention. The packed nanoelectrospray emitter was easily prepared using fused‐silica capillary of 75 μm i.d., and included creating an electrospray emitter tip and then slurry‐packing a 5 cm long column with 5 μm silica‐based particles. After sample loading, the mobile phase was changed for separation and a characteristic precursor‐to‐product ion transition, m/z 275 → 258, was used for the quantification. A linear calibration curve in the range from 1.0–100 ng/mL histamine with an r2 value of 0.9995 was obtained. The detection limit was estimated to be 0.1 ng/mL histamine in water. In a preliminary validation, the method was applied to determine histamine in alcoholic beverages and rat brain tissues. Copyright © 2004 John Wiley & Sons, Ltd.
Automating proteome analysis: improvements in throughput, quality and accuracy of protein identification by peptide mass fingerprinting
Authors: Canelle Ludovic , Pionneau Cédric , Marie Arul , Bousquet Jordane , Bigeard Jean , Lutomski Didier , Kadri Tewfik , Caron Michel , Joubert‐Caron Raymonde 
Published: November 2004

AbstractThe use of robots has major effects on maximizing the proteomic workflow required in an increasing number of high‐throughput projects and on increasing the quality of the data. In peptide mass finger printing (PMF), automation of steps downstream of two‐dimensional gel electrophoresis is essential. To achieve this goal, the workflow must be fluid. We have developed tools using macros written in Microsoft Excel and Word to complete the automation of our platform. Additionally, because sample preparation is crucial for identification of proteins by matrix‐assisted laser desorption/ionization (MALDI) mass spectrometry, we optimized a sandwich method usable by any robot for spotting digests on a MALDI target. This procedure enables further efficient automated washing steps directly on the MALDI target. The success rate of PMF identification was evaluated for the automated sandwich method, and for the dried‐droplet method implemented on the robot as recommended by the manufacturer. Of the two methods, the sandwich method achieved the highest identification success rate and sequence coverage of proteins. Copyright © 2004 John Wiley & Sons, Ltd.
Use of high‐performance liquid chromatography/electrospray ionization collision‐induced dissociation mass spectrometry for structural identification of monohydroxylated progesterones
Authors: Kang Min‐Jung , Lisurek Michael , Bernhardt Rita , Hartmann Rolf W. 
Published: November 2004

AbstractFor the structural identification of monohydroxylated progesterones synthesized by microorganisms, a method was developed using a combination of high‐performance liquid chromatography and electrospray ionization collision‐induced dissociation mass spectrometry (HPLC/ESI‐CIDMS). The retention times and MS/MS spectra of 11 different standards at 30 eV were collected and compared. The identification of D‐ring‐hydroxylated progesterones (15β‐, 16α‐, 17α‐ and 21‐OH‐P) using ESI‐CIDMS was not possible. However, they were separated chromatographically using a 65:35 mixture of water and acetonitrile containing 0.5% acetic acid. The other hydroxylated progesterones (2α‐, 6β‐, 7β‐, 9α‐, 11α‐, 11β‐, and 19‐OH‐P) could be identified by comparison of eight fragments. The complete separation of 11 standards was achieved chromatographically. The developed assay was evaluated by the identification of monohydroxylated progesterones produced by CYP106A2 from Bacillus megaterium ATCC 13368. Copyright © 2004 John Wiley & Sons, Ltd.
Characterization of acylated flavonoid‐O‐glycosides and methoxylated flavonoids from Tagetes maxima by liquid chromatography coupled to electrospray ionization tandem mass spectrometry
Authors: Parejo Irene , Jáuregui Olga , Viladomat Francesc , Bastida Jaume , Codina Carles 
Published: November 2004

AbstractLiquid chromatography coupled to negative electrospray ionization (ESI) tandem mass spectrometry (MS/MS) employing a triple quadrupole mass spectrometer was used in the structural determination of acylated flavonoid‐O‐glycosides and methoxylated flavonoids occurring in Tagetes maxima. The compounds were identified by experiments in full scan mode (MS), and tandem mass experiments (MS/MS) of precursor ion scan, product ion scan, and neutral loss scan modes. In order to characterize the aglycones of the flavonoid glycosides, in‐source fragmentation of the deprotonated molecule [MH]− followed by product ion scan of the resulting aglycone [AH]− were performed. This combined approach allowed the identification of 51 phenolic compounds, including flavonoid‐O‐glycosides acylated with galloyl, protocatechuoyl, coumaroyl or caffeoyl groups, methoxylated flavonoids, and hydroxycinnamic acid and phenolic acid derivatives, none of them previously reported in Tagetes maxima. Copyright © 2004 John Wiley & Sons, Ltd.
Transfer theorems and asymptotic distributional results for m‐ary search trees
Authors: Fill James Allen , Kapur Nevin 
Published: November 2004

AbstractWe derive asymptotics of moments and identify limiting distributions, under the random permutation model on m‐ary search trees, for functionals that satisfy recurrence relations of a simple additive form. Many important functionals including the space requirement, internal path length, and the so‐called shape functional fall under this framework. The approach is based on establishing transfer theorems that link the order of growth of the input into a particular (deterministic) recurrence to the order of growth of the output. The transfer theorems are used in conjunction with the method of moments to establish limit laws. It is shown that: (i) for small toll sequences (tn) [roughly, tn = O(n1/2)] we have asymptotic normality if m ≤ 26 and typically periodic behavior if m ≥ 27; (ii) for moderate toll sequences [roughly, tn = ω(n1/2) but tn = o(n)] we have convergence to nonnormal distributions if m ≤ m0 (where m0 ≥ 26) and typically periodic behavior if m ≥ m0 + 1; and (iii) for large toll sequences [roughly, tn = ω(n)] we have convergence to nonnormal distributions for all values of m. © 2004 Wiley Periodicals, Inc. Random Struct. Alg., 2005
The phase transition in the uniformly grown random graph has infinite order
Authors: Bollobás Béla , Janson Svante , Riordan Oliver 
Published: November 2004

AbstractThe aim of this paper is to study the emergence of the giant component in the uniformly grown random graph Gn(c), 0 < c < 1, the graph on the set[n] = {1, 2, …, n} in which each possible edge ij is present with probability c/ max{i, j}, independently of all other edges. Equivalently, we may start with the random graph Gn(1) with vertex set[n], where each vertex j is joined to each “earlier” vertex i < j with probability 1/j, independently of all other choices. The graph Gn(c) is formed by the open bonds in the bond percolation on Gn(1) in which a bond is open with probability c. The model Gn(c) is the finite version of a model proposed by Dubins in 1984, and is also closely related to a random graph process defined by Callaway, Hopcroft, Kleinberg, Newman, and Strogatz Phys Rev E 64 (2001), 041902. Results of Kalikow and Weiss Israel J Math 62 (1988), 257–268 and Shepp Israel J Math 67 (1989), 23–33 imply that the percolation threshold is at c = 1/4. The main result of this paper is that for c = 1/4 + ϵ, ϵ > 0, the giant component in Gn(c) has order exp(−Θ(1/√ϵ)) n. In particular, the phase transition in the bond percolation on Gn(1) has infinite order. Using nonrigorous methods, Dorogovtsev, Mendes, and Samukhin Phys Rev E 64 (2001), 066110 showed that an even more precise result is likely to hold. © 2004 Wiley Periodicals, Inc. Random Struct. Alg., 2005
Tailor‐Made Nanoparticles via Gas‐Phase Synthesis
Authors: Gutsch Andreas , Mühlenweg Heike , Krämer Michael 
Published: November 2004

AbstractGas‐phase synthesis is a well‐known chemical manufacturing technique for an extensive variety of nanoscale particles. Since the potential of ultrafine and, in particular, nanoscale particles in high‐performance applications has been identified, scientific and commercial interest has increased immensely, thus identifying this field as a most important technology of the future. However, nanomaterials can perform their multifunctional tasks only if they are customized in terms of chemical composition, size, and morphology to suit the application at hand. Profound knowledge of the synthesis and precise process control is crucial in meeting the stringent specifications. Although the gas‐phase synthesis of ultrafine materials has been known and commercially exploited for decades, existing knowledge is based almost exclusively on empirical know‐how. Process simulation is a very suitable tool for expanding the understanding of the synthesis‐relevant processes, particle formation mechanisms, and operating parameters. Based on the resulting expertise some special nanoscale gas‐phase products of high innovative potential have been developed.
On the Development of Colloidal Nanoparticles towards Multifunctional Structures and their Possible Use for Biological Applications
Authors: Pellegrino Teresa , Kudera Stefan , Liedl Tim , Muñoz Javier Almudena , Manna Liberato , Parak Wolfgang J. 
Published: November 2004

AbstractIn this Review, we describe the synthesis of high‐quality colloidal nanoparticles in organic solvents, the mechanisms by which they can be transferred into aqueous solution, and some of their applications in biology. In particular, we will place emphasis on the creation of multifunctional nanoparticles or nanoparticle assemblies.
From Exclusive Xia to Inclusive Zhu-Xia: The Conceptualisation of Chinese Identity in Early China
Authors: Zhi Chen 
Published: November 2004

This paper involves an syncretic study of the structural characteristics, semantic stratification, graphical evolution and contextual analysis on a chronological base of the perplexing graphs and words which designate the Chinese, such as xia, hua and zhongguo, non-Chinese, such as yi, di, rong, and man, in early palaeographic and documentary sources. It shows how these terms evolved to distinguish between the two distinct ethnographical concepts in the early mind.The study shows that the conception of Hua-Xia and Zhongguo carried different connotations in the Western Zhou period from that defined in Spring and Autumn philological sources. The relocation of the Zhou capital to the east during the transition from Western to Eastern Zhou had generically diffused the concept of Xia and the elegant Ya culture. The conception of Xia and Yi, which had formerly distinguished between the Zhou elites and the non-Zhou people, came to distinguish between the central states and peripheral groups in the geographical sense, as well as between the Zhou subjects and the non-Zhou subjects in the political sense. Thus the conceptualisation of the so-called “Chinese-ness” postdates the actual formation of the ethnographical bulk of the Chinese people.
CONFORMAL COUPLING AND INVARIANCE IN DIFFERENT DIMENSIONS
Authors: RAINER MARTIN 
Published: November 2004

Conformal transformations of the following kinds are compared: (1) conformal coordinate transformations, (2) conformal transformations of Lagrangian models for a D-dimensional geometry, given by a Riemannian manifold M with metric g of arbitrary signature, and (3) conformal transformations of (mini-)superspace geometry. For conformal invariance under these transformations the following applications are given respectively: (1) Natural time gauges for multidimensional geometry, (2) conformally equivalent Lagrangian models for geometry coupled to a spatially homogeneous scalar field, and (3) the conformal Laplace operator on the n-dimensional manifold ℳ of minisuperspace for multidimensional geometry and the Wheeler-de Witt equation. The conformal coupling constant ξc is critically distinguished among arbitrary couplings ξ, for both, the equivalence of Lagrangian models with D-dimensional geometry and the conformal geometry on n-dimensional minisuperspace. For dimension D=3, 4, 6 or 10, the critical number [Formula: see text] is especially simple as a rational fraction.