bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crystallographic analysis of an “anticalin” with tailored specificity for fluorescein reveals high structural plasticity of the lipocalin loop region
Authors: Korndörfer Ingo P. , Beste Gerald , Skerra Arne 
Published: August 2003

AbstractThe artificial lipocalin FluA with novel specificity toward fluorescein was derived via combinatorial engineering from the bilin‐binding protein, BBP by exchange of 16 amino acids in the ligand pocket. Here, we describe the crystal structure of FluA at 2.0 Å resolution in the space group P21 with two protein–ligand complexes in the asymmetric unit. In both molecules, the characteristic β‐barrel architecture with the attached α‐helix is well preserved. In contrast, the four loops at one end of the β‐barrel that form the entrance to the binding site exhibit large conformational deviations from the wild‐type protein, which can be attributed to the sidechain replacements. Specificity for the new ligand is furnished by hydrophobic packing, charged sidechain environment, and hydrogen bonds with its hydroxyl groups. Unexpectedly, fluorescein is bound in a much deeper cavity than biliverdin IXγ in the natural lipocalin. Triggered by the substituted residues, unmutated sidechains at the bottom of the binding site adopt conformations that are quite different from those observed in the BBP, illustrating that not only the loop region but also the hydrophobic interior of the β‐barrel can be reshaped for molecular recognition. Particularly, Trp 129 participates in a tight stacking interaction with the xanthenolone moiety, which may explain the ultrafast electron transfer that occurs on light excitation of the bound fluorescein. These structural findings support our concept of using lipocalins as a scaffold for the engineering of so‐called “anticalins” directed against prescribed targets as an alternative to recombinant antibody fragments. Proteins 2003. © 2003 Wiley‐Liss, Inc.
Dispersion of parameters characterizing the Landau levelsin crystals with cubic symmetry
Authors: Olszewski S. , Baszczak M. , Kozak R. 
Published: August 2003

AbstractBroadening of the Landau levels due to the presence of a crystal cubic lattice is examined on a semi‐classical basis for not too strong magnetic fields. The energies of the Landau levels remain discrete also in case of the presence of the lattice potential, but an essential broadening occurs in the momentum space of the electron motion when this motion is limited to a plane being transversal to the applied field. The broadening in the momentum space, attained without any electron–electron interaction admitted for the Landau levels, is described in terms of the band structure parameters characteristic for the presence of the magnetic field. Moreover, for a magnetic field tilted to the crystallographic axes, the broadening is dependent on the inclination angle of the field. Different crystal lattices exhibit different kinds of dispersion. In particular, for the Landau levels of tightly‐bound s‐electrons in a simple cubic and body‐centred cubic lattice there is no dispersion in the electron gyration frequency and degeneracy number of the level area over the value of the wavevector component parallel to the magnetic field. On the other hand, this kind of dispersion exists in the case of the face‐centred cubic lattice.
VUV spectroscopy of pure and Sm2+ doped SrFCl crystals
Authors: Kisand Vambola , Kink Rein , Kink Ilmar , Jaaniso Raivo , Martinson Indrek 
Published: August 2003

AbstractThe creation and relaxation of electronic excitations in pure crystalline SrFCl and Sm2+ doped SrFCl were investigated using vacuum ultraviolet (VUV) spectroscopic methods. In the emission spectra of pure SrFCl and SrFCl : Sm2+ a strong emission band in the vicinity of 4.7 eV was detected, connected to self‐trapped exciton (STE) having a Cl2− core. The threshold for creation of STE was detected at 8.5 eV in the excitation spectrum of pure SrFCl and at 7.6 eV for Sm2+ doped SrFCl. It was demonstrated that the excitation spectrum of Sm2+ emission is determined with direct excitation of a Sm2+ center below 7.6 eV and with excitation of the SrFCl host above 7.6 eV.
New sum rules relating the 1‐body momentum distribution of the homogeneous electron gas to the Kimball–Overhauser 2‐body wave functions (geminals) of its pair density
Authors: Ziesche P. , Pernal K. , Tasnádi F. 
Published: August 2003

AbstractRecently, new sum rules for the scattering phase shifts of the pair‐density geminals (being 2‐body‐wave functions which parametrize the pair density together with an appropriately chosen occupancy) have been derived from the normalization of the pair density [P. Ziesche, Phys. Rev. B 67, 233102 (2003)]. Here, we present a generalization of these sum rules, which allows one in principle to calculate the momentum distribution from these geminals and their phase shifts. These contraction sum rules contain the afore mentioned (Friedel‐like) normalization sum rules as special cases.
Crystal field analysis of erbium doped yttrium oxide thin films in C2 and C3i sites
Authors: Dammak M. , Maalej R. , Kamoun M. , Deschanvres J.‐L. 
Published: August 2003

AbstractFluorescence measurements on Er ions in Y2O3 thin films have been analyzed with crystal‐field Hamiltonians of C2 and C3i symmetries including J‐mixing effects. Crystal‐field parameters have been determined based on the Racah theory, that minimize the rms deviation between calculated and experimentally found energy. This theoretical analysis confirms the dominance of the C2 symmetry site in the fluorescence spectrum; however in the infrared emission spectrum, the contribution of the two sites C2 and C3i is comparable.
Spin dephasing in n‐type GaAs quantum wells in the presence of high magnetic fields in Voigt configuration
Authors: Weng M. Q. , Wu M. W. 
Published: August 2003

AbstractWe perform a many‐body study of the spin dephasing due to the D'yakonov–Perel' (DP) effect in n‐type GaAs (100) quantum wells under high magnetic fields in the Voigt configuration by constructing and numerically solving the kinetic Bloch equations. We include all spin‐conserving scattering, such as electron–phonon, electron–non‐magnetic impurity as well as electron–electron Coulomb scattering, in our theory and investigate how the spin dephasing time (SDT) is affected by the initial spin polarization, impurity, and magnetic field. The dephasing obtained from our theory contains not only that due to the effective spin‐flipping scattering first proposed by DP [M. I. D'yakonov and V. I. Perel', Zh. Eksp. Teor. Fiz. 60, 1954 (1971); Sov. Phys. – JETP 38, 1053 (1971)], but also the recently proposed many‐body dephasing due to the inhomogeneous broadening provided by the DP term [M. W. Wu, J. Supercond.: incorp. Novel Mechanism 14, 245 (2001); M. W. Wu and C. Z. Ning, Eur. Phys. J. B 18, 373 (2000)]. We are able to investigate the spin dephasing with extra‐large spin polarization (up to 100%), which has not been discussed either theoretically or experimentally. A huge anomalous resonance of the SDT for large spin polarizations is predicted under the high magnetic field we used. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comment on “Some considerations concerning the detection of excitons by field ionization in a Schottky barrier” – [phys. stat. sol. (b) 234, No. 1, 23–35 (2002)]
Authors: Mysyrowicz A. , Leblanc P. J. , Fortin E. 
Published: August 2003

AbstractWe revisit the detection of excitons in Cu2O by the exciton‐mediated effect. It is shown that this type of detector is linear over a wide range of exciton densities, contrary to a recent claim that it should quickly saturate. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Response to “Comment on ‘Some considerations concerning the detection of excitons by field ionization in a Schottky barrier’” – [phys. stat. sol. (b)239, No. 1, 257–260 (2003)]
Authors: Klingshirn C. , Fleck T. , Jörger M. 
Published: August 2003

AbstractA photocurrent signal and its temporal dependence on the excitation conditions observed in a Cu/Cu2O Schottky barrier after pulsed illumination of the Cu2O crystal has been used to claim excitonic superfluidity and Bose‐Einstein condensation. See, e.g., E. Benson, E. Fortin, and A. Mysyrowicz [phys. stat. sol. (b)191, 345 (1995)]. C. Klingshirn, T. Fleck, and M. Jörger [phys. stat. sol. (b)234, 23 (2002)] showed that a similar behaviour can be expected also from detector saturation which is very likely for the excitation conditions used in the above work. In the above comment [phys. stat. sol. (b)239, 257 (2003)], these arguments have been rejected, based on new experiments under resonant exciton creation. In this response we show that the excitation conditions used in these new experiments do not allow to question the statements in favour of detector saturation, but raise some additional questions. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Strain effects in large‐scale atomistic quantum dot simulations
Authors: Oyafuso Fabiano , Klimeck Gerhard , von Allmen Paul , Boykin Tim , Bowen R. Chris 
Published: August 2003

AbstractAtomistic computations of electronic properties for nanostructures with strain (such as self‐assembled quantum dots) typically consist of two components – a calculation of the individual atomic positions and the eigenstates of interest in the resulting Hamiltonian. Such simulations ultimately require artificial boundary conditions either through a truncation of the simulation domain or by the imposition of periodic boundary conditions, which necessarily introduce inaccuracies in both components of the computation. In simulations that include up to about 20 million atoms, it is demonstrated that the simulation domain truncation has little impact on the direct computation of the electronic energies but causes considerable inaccuracies in the calculation of the atomic positions unless the simulation domain is made much larger than the central quantum dot structure. The long‐range nature of the lattice distortions induced by lattice mismatch is consequently expected to significantly alter the electronic structure of nearby quantum dots. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Phenomenological theory to model leakage currents in metal–insulator–metal capacitor systems
Authors: Ramprasad R. 
Published: August 2003

AbstractA phenomenological model intended to provide a description of leakage behavior in metal–insulator–metal (MIM) capacitor devices is presented. The model is able to predict both transient and steady state leakage currents under constant voltage bias conditions (the J–t characteristics), as well as J–V characteristics for a given voltage sweep schedule. The electronic transport processes currently implemented in the model include trap assisted tunneling (TAT) of electrons from the electrode to defect or trap states in the dielectric, modified Poole–Frenkel (MPF) emission of part of the trapped electrons to the conduction band of the dielectric, and Schottky emission of Fermi level electrons directly from the electrode to the conduction band of the dielectric. The model is able to predict many of the observed features, including characteristic slopes in J–t and J–V plots, and dependences of the leakage current on dielectric thickness, temperature and the Schottky barrier height. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical excitations in small hydrogenated silicon clusters: comparison of theory and experiment
Authors: Vasiliev Igor 
Published: August 2003

AbstractExcitation energies and absorption spectra of small hydrogenated silicon clusters are calculated within the framework of time‐dependent density‐functional response theory. The calculations employ several different approximations for the exchange‐correlation kernel, including the local density approximation as well as asymptotically correct Leeuwen–Baerends and Casida–Salahub potentials. The structures of the theoretical spectra are analyzed in detail and the positions of the absorption peaks obtained with different exchange‐correlation kernels are matched to the available experimental data based on the oscillator strength and symmetry of electronic transitions. The calculated absorption gaps are compared to the experimental values and discussed in terms of the applicability of common theoretical and experimental definitions for optical gaps to small clusters. (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Assessing the Effect of Time in Factorial Designs: The Practical Application
Authors: Chatfield M. J. , Owen M. R. 
Published: August 2003

AbstractThe scientist asks a statistician the question: ‘should we incorporate time as a factor in our factorial designs or measure the response at various time‐points?’ Advantages and disadvantages of the approaches are discussed. The aspects to be considered include: the relative costs of performing the experiment, the response measurement and the statistical analysis; the quality of the data collected and the information to be gained from the experimentation; implications for possible designs; implications for setting up, analysis and interpretation of designs in standard software available to scientists; and pitfalls to avoid. The field of chemical process investigation is used to illustrate some of the issues involved. In some scientific areas the experimental or resource issues may be overriding and the answer obvious. For the chemist, in some cases the only choice will be the factorial design which includes time as a factor due to experimental reasons but in most cases the appropriate answer depends on careful consideration of the aspects listed above. The paper illustrates the importance of a partnership between scientist and statistician in addressing the practical application of statistical techniques. Copyright © 2003 John Wiley & Sons, Ltd.
Bayesian Analysis and Prediction of Failures in Underground Trains
Authors: Pievatolo Antonio , Ruggeri Fabrizio , Argiento Raffaele 
Published: August 2003

AbstractBased upon failure data (date and odometer reading) in the early operating time, a public transportation company is interested in checking the actual reliability of the door opening system of its subway trains before their warranty expires. We consider non‐homogeneous Poisson processes with a double scale because both time and kilometres are recorded for each failure. Different choices to model the relation between operated time and kilometres run are possible: in this paper the kilometres run are incorporated within the intensity function as a random function of time, modelled as a gamma process. Furthermore a periodic component is introduced to deal with the seasonality in the data. Bayesian inference is then carried out via Monte Carlo simulation, obtaining prediction intervals for the expected number of failures during periods of desired length, using only part of the data. The predictions are then compared with the observed data. Copyright © 2003 John Wiley & Sons, Ltd.
A Comparison of Shewhart Individuals Control Charts Based on Normal, Non‐parametric, and Extreme‐value Theory
Authors: Vermaat M. B. (Thijs) , Ion Roxana A. , Does Ronald J. M. M. , Klaassen Chris A. J. 
Published: August 2003

AbstractSeveral control charts for individual observations are compared. Traditional ones are the well‐known Shewhart individuals control charts based on moving ranges. Alternative ones are non‐parametric control charts based on empirical quantiles, on kernel estimators, and on extreme‐value theory. Their in‐control and out‐of‐control performance are studied by simulation combined with computation. It turns out that the alternative control charts are not only quite robust against deviations from normality but also perform reasonably well under normality of the observations. The performance of the Empirical Quantile control chart is excellent for all distributions considered, if the Phase I sample is sufficiently large. Copyright © 2003 John Wiley & Sons, Ltd.
Simulation Models for Robust Design Using Location Depth Methods
Authors: Stadlober Ernst , Kocher Michael , Rappitsch Gerhard 
Published: August 2003

AbstractFor a cost‐effective production of integrated circuits, one important aspect is the accurate simulation of electronic circuits with regard to process variation. Process variation is described as the range of simulation (SPICE) parameters, but to reduce the costs of simulation they are replaced by easily available e‐test parameters. An approximate algorithm for the location depth (multivariate ranking) selects all data points with location depth less than or equal to one as boundary points for the multidimensional data set of e‐test parameters. The corresponding SPICE parameter values are simply obtained by linear mapping. To increase the robustness of the simulation the region covered by the set of boundary points is extended by determining the point with the deepest location (multivariate median) and adding to each boundary vector a fixed portion of the vector from the median to the boundary vector. This natural extension also covers moderate process shifts without changing the covariance structure of the data. These methods are integrated into an automated generation flow to be applicable in a production and circuit design environment. The statistical methods are validated by simulation experiments of typical analog/mixed‐signal circuit designs. Copyright © 2003 John Wiley & Sons, Ltd.
Visually Mining Off‐line Data for Quality Improvement
Authors: Porzio Giovanni C. , Ragozini Giancarlo 
Published: August 2003

AbstractHighly automated modern manufacturing processes are yielding large databases with records on hundreds of process variables and product characteristics. This large amount of information calls for new approaches to production process analysis. In this paper, we discuss why a data mining framework can be appropriate for this goal, and we propose a visual data mining strategy to mine large and high‐dimensional off‐line data sets. The strategy allows users to achieve a deeper process understanding through a set of linked interactive graphical devices, and is illustrated within an industrial process case study. Copyright © 2003 John Wiley & Sons, Ltd.
Change Point Estimates for the Parameters of an AR(1) Process
Authors: Timmer Douglas H. , Pignatiello Joseph J. 
Published: August 2003

AbstractThree change point estimates for the parameters of a first‐order autoregressive (AR(1)) model are developed. The estimators are applied once a control chart signals indicating the presence of a special or assignable cause of variability. The knowledge of the change point can greatly aid the quality practitioner in identifying and removing special causes of variability. Techniques for determining the change point for the location of the AR(1) process, the variance of the white noise process and the autoregressive parameter changed are presented. Simulation results are provided to evaluate the effectiveness of the three change point estimators. Copyright © 2003 John Wiley & Sons, Ltd.
Turán's theorem in sparse random graphs
Authors: Szabó Tibor , Vu Van H. 
Published: August 2003

AbstractWe prove the analogue of Turán's Theorem in random graphs with edge probability p(n) ≫ n−1/(k−1.5). With probability 1 − o(1), one needs to delete approximately ‐fraction of the edges in a random graph in order to destroy all cliques of size k. © 2003 Wiley Periodicals, Inc. Random Struct. Alg., 23: 225–234, 2003
On the distribution of the number of roots of polynomials and explicit weak designs
Authors: Hartman Tzvika , Raz Ran 
Published: August 2003

AbstractWeak designs were defined in R. Raz, O. Reingold, and S. Vadhan [Extracting all the randomness and reducing the error in Trevisan's extractors, Proc 31st ACM Symp Theory of Computing, Atlanta, GA, May 1999, to appear in J Comput System Sci Special Issue on STOC 99] and are used there in constructions of extractors. Roughly speaking, a weak design is a collection of subsets satisfying some near‐disjointness properties. Constructions of weak designs with certain parameters are given in Raz et al. These constructions are explicit in the sense that they require time and space polynomial in the number of subsets. However, the constructions require time and space polynomial in the number of subsets even when needed to output only one specific subset out of the collection. Hence, the constructions are not explicit in a stronger sense. In this work we provide constructions of weak designs (with parameters similar to the ones of Raz et al.) that can be carried out in space logarithmic in the number of subsets. Moreover, our constructions are explicit even in a stronger sense: Given an index to a subset, we output the specified subset in time and space polynomial in the size of the index. Using our constructions, we obtain extractors similar to some of the ones given in Raz et al. in terms of parameters, and that can be evaluated in logarithmic space. Our main construction is algebraic. In order to prove the properties of weak designs, we prove some algebro‐combinatorial lemmas that may be interesting in their own right. These lemmas regard the number of roots of polynomials over finite fields. In particular, we prove that the number of polynomials (over any finite field) withkroots, vanishes exponentially ink.In other words, we prove that the number of roots of a random polynomial is not only bounded by its degree (a well‐known fact), but, furthermore, it is concentrated exponentially around its expectation (which is 1). Our lemmas are proved by algebro‐combinatorial arguments. The main lemma is also proved by a probabilistic argument. © 2003 Wiley Periodicals, Inc. Random Struct. Alg., 23: 235–263, 2003
Feed‐forward and recurrent neural networks for source code informal information analysis
Authors: Merlo Ettore , McAdam Ian , De Mori Renato 
Published: August 2003

AbstractDesign recovery, which is a part of the reverse engineering process of source code, must supply programmers with all the information they need to fully understand a program or a system. In this paper, a connectionist method that can be used for design recovery in conjunction with more traditional approaches is proposed for analyzing the informal information (comments and mnemonics) in programs. An approach based on artificial neural networks (ANNs) was chosen because of its property of being robust (capable of tolerating noisy inputs), because of its associative memory ability (capable of retrieving a concept given only the context of the input word that originally fired the concept), and because of its generalization power (ability to learn conceptually relevant micro‐features of the domain). The proposed approach uses a combination of top down domain analysis (i.e., the creation of a concept hierarchy by a domain expert, to be used in the construction of the training set) and a bottom up approach (i.e., the analysis of the informal information using ANNs).A preprocessing system that extracts the relevant comments and identifier names and transforms them into an input for the ANNs has been developed. Feed‐forward neural networks (FNNs) and recurrent neural networks (RNNs) were tried. RNN architectures are capable of learning sequences and are able to make use of the word ordering of the sentence. The networks were trained on part of the source code of an existing system and tested on a different portion of the system code. Test results, consisting of coverage and evaluation figures, are presented. They show a remarkably higher accuracy when ANNs, in general, are used as opposed to simple lexical methods. RNNs, in particular, also show higher coverage and accuracy than FNNs. Copyright © 2003 John Wiley & Sons, Ltd.