bluuebunny/crossref_metadata_2025_split huggingface dataset:
Continuous amorphization of Cu–Zr studied by positron lifetime and two‐dimensional Doppler broadening measurements
Authors: Puff W. , Rabitsch H. , Würschum R. , Wilde G. 
Published: August 2007

AbstractPositron lifetime and 2‐dimensional Doppler broadening measurements were used to study the amorphization of Cu60Zr40 induced by consecutive folding and rolling. In an intermediate state of folding and rolling cycles a complex microstructure evolves with structural free volumes exhibiting a local environment with enhanced Zr content. In the fully amorphous state after 80 cycles, free volumes of the size of a few missing atoms occur which is contrast to amorphous alloys prepared by melt‐spinning. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Pulsed low energy positron system (PLEPS) at the Munich research reactor FRM II
Authors: Egger W. , Sperr P. , Kögel G. , Dollinger G. 
Published: August 2007

AbstractCurrently, the Munich pulsed low energy positron beam‐system (PLEPS) is transferred to the high‐intensity positron source (NEPOMUC) at the Munich research Reactor FRM II. We expect count‐rates up to 106 cps. Several improvements to enhance the performance of the system have been implemented. Until now, PLEPS was employed exclusively for lifetime measurements. To enable also Doppler‐broadening, coincident Doppler‐broadening and AMOC experiments, two additional detector ports have been installed. An additional chopper allows to suppress pulses and, therefore, to extend the standard time window of 20 ns for precise measurements of longer lifetimes. The high event‐rate supports the use of smaller scintillators. Consequently an improvement in time resolution is expected. Also envisaged is the use of new detector materials. Various measures to further reduce background from back‐scattered positrons and a reduction of the beam diameter down to 1 mm will improve the overall performance of the system. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Digital positron lifetime spectrometer for measurements of radioactive materials
Authors: Jardin M. , Almazouzi A. , Lambrecht M. , Rempel A. , Nagai Y. , van Walle E. 
Published: August 2007

AbstractA digital positron lifetime spectrometer for the measurements of 2 GBq level radioactive materials has been constructed and successfully tested. The equipment consists of a state‐of‐the‐art digital oscilloscope and three movable scintillation detectors operating in triple‐coincidence mode. The time resolution of 188 ps full‐width at half‐maximum (FWHM) is achieved for the positron lifetime measurements of radioactive specimens. Also by comparison of measurements of well‐known material with and without high 60Co background radiation the ability to measure radioactive specimens is proved. In this paper the performance, construction, installation, optimization and calibration of the setup is reported. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
MBE growth of dilute magnetic (Zn,Mn)Se on Si substrates
Authors: Slobodskyy A. , Keller D. , Gould C. , Ossau W. , Schmidt G. , Molenkamp L. W. 
Published: August 2007

AbstractWe have demonstrated growth of the dilute magnetic II–VI semiconductor (Zn,Mn)Se on As‐passivated (100) oriented Si substrates. Low temperature epitaxy has been used to optimize the growth start. The morphology has been assessed by Nomarski and scanning electron microscopy (SEM). SQUID measurements show the full magnetic moment of the Mn ions and optical investigations show a clear Zeeman splitting of up to 30 meV. All observations indicate a high crystalline quality of the epitaxial layers. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Phase effects in HgTe quantum structures
Authors: König M. , Buhmann H. , Becker C. R. , Molenkamp L. W. 
Published: August 2007

AbstractHgTe quantum well structures with high electron mobilities have been used to fabricate quantum interference devices. Aharonov‐Bohm oscillations have been studied in the low and high magnetic field regime. In the latter case a decrease of the effective ring radius is observed. Additionally, as a consequence of the strong Rashba spin‐orbit coupling within this material, it was possible to observe conductance oscillations which are due to the so‐called Aharonov‐Casher effect. These quantum interference effects are effectively controlled by the applied magnetic and electric field. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of liquid‐phase synthesis parameters on particle sizes and structural properties of nanocrystalline ZnO powders
Authors: Chory Christine , Neder Reinhard B. , Korsunskiy Vladimir I. , Niederdraenk Franziska , Kumpf Christian , Umbach Eberhard , Schumm Marcel , Lentze Michael , Geurts Jean , Astakhov Georgy , Ossau Wolfgang , Müller Gerd 
Published: August 2007

AbstractIn order to obtain well‐controlled size and optimized structural properties, ZnO nanoparticles were grown from ethanolic solutions using acetate, acetylacetonate and dimethylpropylendiamine as stabilizer molecules. The low‐temperature syntheses yield considerably large amounts of pure, nanocrystalline powder. Structural properties like particle size, crystal structure and quality were investigated by x‐ray diffractometry, photoluminescence, and Raman spectroscopy. Particle sizes down to 4 nm and a size dependent anisotropic shape are observed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A weighted logistic regression for conjoint analysis and Kansei engineering
Authors: Barone Stefano , Lombardo Alberto , Tarantino Pietro 
Published: August 2007

AbstractCustomer needs for emotional satisfaction are increasingly being considered by product and service designers. While several existing methods such as conjoint analysis (CA), Kano model and quality function deployment support the translation of customer requirements into technical specifications, researchers are now working to develop methods aimed at integrating affective aspects into product design. Kansei engineering (KE) is a design philosophy that considers customer perceptions and emotions by adopting a multi‐disciplinary approach. CA is a useful tool within a KE project. This article presents a methodology for conducting a KE project in early development phases. This methodology is based on two new procedures. The first one is aimed at calculating attribute importance weights by using respondent choice time in controlled interviews. The second procedure allows the exploitation of such weights in an ordinal logistic regression model for analysing the results of CA experiments. By using the proposed methodology, it is possible to identify product/service attributes able to induce specific emotions and feelings in customers and consequently choose the right development strategy. An application of the method for the design of mobile phones is presented. Copyright © 2007 John Wiley & Sons, Ltd.
Effect of exposure misclassification on the mean squared error of population attributable risk and prevented fraction estimates
Authors: Walter S. D. , Hsieh C. C. , Liu Qin 
Published: August 2007

AbstractPrevious work has considered the effect of exposure misclassification on the bias of population attributable risk (AR) estimates, but little is known about the corresponding effects on their precision or mean squared error (MSE). This paper considers AR estimation in typical scenarios for case–control and cohort studies. The analogous index used when exposure reduces the risk—the prevented fraction (PF)—is also investigated.It is shown, through both theoretical and simulation results, that even with quite modest levels of exposure misclassification, the MSE can increase substantially, relative to the variance of AR estimated without measurement error. When exposure assessment is perfectly sensitive, there is no bias in AR but lack of measurement specificity can still cause a substantial loss of precision. In a few cases, the AR or PF with misclassified exposure can actually have smaller MSE; these exceptional cases arise when sensitivity is poor and the bias in AR or PF is relatively large.We conclude that while bias can be reduced by defining exposure on a highly sensitive basis, one must also consider the deleterious effect on precision by doing so. Loss of precision in the AR and PF estimates can be safely ignored only when the exposure measure is very accurate. Copyright © 2007 John Wiley & Sons, Ltd.
Mediation analysis via potential outcomes models
Authors: Albert Jeffrey M. 
Published: August 2007

AbstractThis paper develops a causal or manipulation model framework for mediation analysis based on the concept of potential outcome. Using this framework, we provide new definitions and measures of mediation. Effects of manipulations are modeled via the linear structural model. Corresponding structural equation models (SEMs), in conjunction with two‐stage least‐squares estimation and the delta method, are used to perform inference. The methods are applied to data from a study of nursing interventions for postoperative pain. We address the cases of more than two treatment groups, and an interaction among mediators. For the latter, a sensitivity analysis approach to handle unidentified parameters is described. Interpretative advantages of the potential outcomes framework for mediation are emphasized. Copyright © 2007 John Wiley & Sons, Ltd.
Comparing several means of dependent populations of count—A parametric robust approach
Authors: Tsou Tsung‐Shan , Chen Chien‐Hung 
Published: August 2007

AbstractWe propose a parametric robust procedure for comparing several means of dependent populations of counts. The validity of the proposed method requires no knowledge of the true underlying joint distributions so long as they have finite second moments. The efficacy of this novel technique is demonstrated by simulations and the analysis of a data set from the Taiwan National Health Insurance Research Database. Our new parametric robust method is also compared with the popular semi‐parametric generalized estimating equations approach. Copyright © 2007 John Wiley & Sons, Ltd.
Submonolayer Quantum Dots for High Speed Surface Emitting Lasers
Authors: Ledentsov NN , Bimberg D , Hopfer F , Mutig A , Shchukin VA , Savel’ev AV , Fiol G , Stock E , Eisele H , Dähne M , Gerthsen D , Fischer U , Litvinov D , Rosenauer A , Mikhrin SS , Kovsh AR , Zakharov ND , Werner P 
Published: August 2007

AbstractWe report on progress in growth and applications of submonolayer (SML) quantum dots (QDs) in high-speed vertical-cavity surface-emitting lasers (VCSELs). SML deposition enables controlled formation of high density QD arrays with good size and shape uniformity. Further increase in excitonic absorption and gain is possible with vertical stacking of SML QDs using ultrathin spacer layers. Vertically correlated, tilted or anticorrelated arrangements of the SML islands are realized and allow QD strain and wavefunction engineering. Respectively, both TE and TM polarizations of the luminescence can be achieved in the edge-emission using the same constituting materials. SML QDs provide ultrahigh modal gain, reduced temperature depletion and gain saturation effects when used in active media in laser diodes. Temperature robustness up to 100 °C for 0.98 μm range vertical-cavity surface-emitting lasers (VCSELs) is realized in the continuous wave regime. An open eye 20 Gb/s operation with bit error rates better than 10−12has been achieved in a temperature range 25–85 °Cwithout current adjustment. Relaxation oscillations up to ∼30 GHz have been realized indicating feasibility of 40 Gb/s signal transmission.
Strain Relief Analysis of InN Quantum Dots Grown on GaN
Authors: Lozano Juan G , Sánchez Ana M , García Rafael , Ruffenach Sandra , Briot Olivier , González David 
Published: August 2007

Abstract
We present a study by transmission electron microscopy (TEM) of the strain state of individual InN quantum dots (QDs) grown on GaN substrates. Moiré fringe and high resolution TEM analyses showed that the QDs are almost fully relaxed due to the generation of a 60° misfit dislocation network at the InN/GaN interface. By applying the Geometric Phase Algorithm to plan-view high-resolution micrographs, we show that this network consists of three essentially non-interacting sets of misfit dislocations lying along the "Equation missing" directions. Close to the edge of the QD, the dislocations curve to meet the surface and form a network of threading dislocations surrounding the system.
Screw placement in slipped upper femoral epiphysis: Is good the enemy of better?
Authors: Jamil Wiqqas , Allami Mohamad K. , Varghese Bobin , Almaiyah Mohammed , Giannoudis Peter 
Published: August 2007

Introduction and aims A single hip screw is the recommended method of fixation for slipped upper femoral epiphysis (SUFE). Current practice favours the placement of the screw in the centre of the femoral head on both anteroposterior and lateral planes to avoid the risks of chondrolysis and avascular necrosis (AVN). We investigated the correlation between different positions of the screw in the femoral head and the prevalence of AVN, chondrolysis, late slippage and the time to epiphyseal closure. Methods The clinical notes and radiographs of 38 consecutive patients (61 hips) who underwent single screw fixation for SUFE were evaluated retrospectively with a mean follow-up of 36 months. Two-way ANOVA and the post hoc test was performed to analyse the correlation between the different variables and the outcome at the 5% level of significance. Results There were 16 acute slips, 18 chronic slips and ten acute-on-chronic slips. Seventeen slips were treated prophylactically. Mild slip was encountered in 39 hips, moderate slip in four and severe slip in one. The central–central position was only achieved in 51% of cases. The most significant results of the study were as follows: (1) no significant difference between the time to epiphyseal closure and the position of the screw, and (2) no late slippage or chondrolysis was observed in our series. Conclusion Our results showed that the positioning of the screw other than in the centre of the femoral head has the ability to provide physeal stability and has no correlation with the timing to closure of the epiphysis and the risk of avascular necrosis or chondrolysis. We therefore recommend that other positions be considered if the “optimal central–central position” is not initially achieved – specifically for the treatment of mild slip – as the potential hazards from several attempts to achieve the optimum position outweigh the benefits.
ON AN OPEN QUESTION OF RICCERI CONCERNING A NEUMANN PROBLEM
Authors: FARACI FRANCESCA , KRISTÁLY ALEXANDRU 
Published: August 2007

AbstractIn this paper we solve partially an open problem raised by B. Ricceri (Bull. London Math. Soc.33 (2001), 331–340). Infinitely many solutions for a Neumann problem are obtained through a direct variational approach where the nonlinearity has an oscillatory behaviour at infinity.
NOTE ON A PAPER OF J. HOFFSTEIN
Authors: PATTERSON S. J. 
Published: August 2007

AbstractThe concept of a metaplectic form was introduced about 40 years ago by T. Kubota. He showed how Jacobi-Legendre symbols of arbitrary order give rise to characters of arithmetic groups. Metaplectic forms are the automorphic forms with these characters. Kubota also showed how higher analogues of the classical theta functions could be constructed using Selberg's theory of Eisenstein series. Unfortunately many aspects of these generalized theta series are still unknown, for example, their Fourier coefficients. The analogues in the case of function fields over finite fields can in principle be calculated explicitly and this was done first by J. Hoffstein in the case of a rational function field. Here we shall return to his calculations and clarify a number of aspects of them, some of which are important for recent developments.
PROPERTIES OF CERTAIN SUBALGEBRAS OF DALES-DAVIE ALGEBRAS
Authors: ABTAHI M. , HONARY T. G. 
Published: August 2007

AbstractWe study an interesting class of Banach function algebras of infinitely differentiable functions on perfect, compact plane sets. These algebras were introduced by H. G. Dales and A. M. Davie in 1973, called Dales-Davie algebras and denoted by D(X, M), where X is a perfect, compact plane set and M = {Mn}∞n = 0 is a sequence of positive numbers such that M0 = 1 and (m + n)!/Mm+n ≤ (m!/Mm)(n!/Mn) for m, n ∈ N. Let d = lim sup(n!/Mn)1/n and Xd = {z ∈ C : dist(z, X) ≤ d}. We show that, under certain conditions on X, every f ∈ D(X, M) has an analytic extension to Xd. Let DP [DR]) be the subalgebra of all f ∈ D(X, M) that can be approximated by the restriction to X of polynomials [rational functions with poles off X]. We show that the maximal ideal space of DP is $X^_d$, the polynomial convex hull of Xd, and the maximal ideal space of DR is Xd. Using some formulae from combinatorial analysis, we find the maximal ideal space of certain subalgebras of Dales-Davie algebras.
POSITIVE SOLUTIONS FOR ASYMPTOTICALLY LINEAR ELLIPTIC SYSTEMS
Authors: PENG CHAOQUAN , YANG JIANFU 
Published: August 2007

AbstractIn this paper, we show that the semilinear elliptic systems of the form
(0.1)
possess at least one positive solution pair (u, v) ∈ H10(Ω) × H10(Ω), where Ω is a smooth bounded domain in $\mathbb{R}^N$, f(x,t) and g(x, t) are continuous functions on $\Omega\times \mathbb{R}$ and asymptotically linear at infinity.
HARDY–BLOCH TYPE SPACES AND LACUNARY SERIES ON THE POLYDISK
Authors: AVETISYAN K. L. 
Published: August 2007

AbstractWe extend the well-known Paley and Paley-Kahane-Khintchine inequalities on lacunary series to the unit polydisk of $\C^n$. Then we apply them to obtain sharp estimates for the mean growth in weighted spaces h(p, α), h(p, log(α)) of Hardy–Bloch type, consisting of functions n-harmonic in the polydisk. These spaces are closely related to the Bloch and mixed norm spaces and naturally arise as images under some fractional operators.
MORSE INEQUALITIES ON CERTAIN INFINITE 2-COMPLEXES
Authors: AYALA R. , FERNÁNDEZ L. M. , VILCHES J. A. 
Published: August 2007

AbstractUsing the notion of discrete Morse function introduced by R. Forman for finite cw-complexes, we generalize it to the infinite 2-dimensional case in order to get the corresponding version of the well-known discrete Morse inequalities on a non-compact triangulated 2-manifold without boundary and with finite homology. We also extend them for the more general case of a non-compact triangulated 2-pseudo-manifold with a finite number of critical simplices and finite homology.
ON THE SQUARE-FREE PARTS OF ⌊en!⌋
Authors: LUCA FLORIAN , SHPARLINSKI IGOR E. 
Published: August 2007

AbstractIn this note, we show that if we write ⌊en!⌋ = s(n)u(n)2, where s(n) is square-free then

has at least C log log N distinct prime factors for some absolute constant C > 0 and sufficiently large N. A similar result is obtained for the total number of distinct primes dividing the mth power-free part of s(n) as n ranges from 1 to N, where m ≥ 3 is a positive integer. As an application of such results, we give an upper bound on the number of n ≤ N such that ⌊en!⌋ is a square.
A Difference Test Method for Early Detection of Slowly Growing Errors in GNSS Positioning
Authors: Feng Shaojun , Ochieng Washington 
Published: August 2007

Satellite based navigation system integrity monitoring is essential both for liability and safety critical services. The threats to system integrity are the potential failure modes that could occur at system, operational and user sensor levels. Research on identification, characterisation and modelling of such failure modes, suggests that failures that grow slowly over time (e.g. ramp error less than 2 m/s), also referred to as slowly growing errors (SGE) are the most difficult to detect early. Conventional snapshot algorithms detect SGEs when the test statistic crosses the threshold usually after relatively long periods of time. A recent concept based on the average of residuals over time has been found to have a significant weakness. This paper proposes a “difference test” algorithm capable of detecting SGEs early. In this method, the test statistic is the difference between the norm of current residuals and the norm of the residuals at a previous epoch. The distribution of the test statistic is over-bounded by a normal distribution whose parameters are derived from two Chi-distributions. Results show that the new algorithm results in a significant reduction in detection time compared to conventional methods.
Investigations into Phase Multipath Mitigation Techniques for High Precision Positioning in Difficult Environments
Authors: Lau Lawrence , Cross Paul 
Published: August 2007

The modelling of most Global Navigation Satellite System (GNSS) errors/biases and developments of data processing techniques have been improved substantially since the birth of Global Positioning System (GPS), however, there has been much less progress in the improvement of phase multipath mitigation techniques. Multipath therefore remains one of the most important error sources in high precision GNSS positioning. This is because multipath is site-dependent and therefore cannot be eliminated by differencing techniques. Also multipath is highly dependent on satellite-reflector-antenna geometry, which usually causes rapid changes in phase multipath errors especially in Real-Time Kinematic (RTK) applications. Multipath mitigation for static antennas such as those at reference stations can be carried out by site calibration, averaging over long observation times, and through the estimation of the error using filtering based on signal-to-noise ratio (SNR) data. However, multipath mitigation for kinematic antennas is still very difficult today.Nevertheless, much research has been carried out on a particular class of phase multipath mitigation techniques: ones that can be applied within positioning algorithms (rather than incorporated into the receiver tracking loops or antennas). This paper investigates and further develops a number of state-of-the-art techniques in this category. They include phase multipath estimation using SNR data, phase multipath estimation through the use of closely spaced antennas, multipath mitigation stochastic models such as the satellite elevation angle model and SNR-based models (SIGMA-∊ model and our modified SNR-based model), and our own novel ray-tracing method. The techniques are tested with both real and simulated data, the real test datasets have been collected on the Laboratoire Central des Ponts et Chaussées (LCPC) testbed near Nantes in France, and on the campus of the University of Nottingham during SPACE data collection experiments.
Part II. Analysis of data gaps pertaining toShigellainfections in low and medium human development index countries, 1984–2005
Authors: RAM P. K. , CRUMP J. A. , GUPTA S. K. , MILLER M. A. , MINTZ E. D. 
Published: August 2007

SUMMARYThe global incidence ofShigellainfection has been estimated at 80–165 million episodes annually, with 99% of episodes occurring in the developing world. To identify contemporary gaps in the understanding of the global epidemiology of shigellosis, we conducted a review of the English-language scientific literature from 1984 to 2005, restricting the search to low and medium human development countries. Our review yielded 11 population-based studies ofShigellaburden from seven countries. No population-based studies have been conducted in sub-Saharan Africa or in low human development countries. In studies done in all age groups,Shigellaincidence varied from 0·6 to 107 episodes/1000 person-years.S. flexneriwas the most commonly detected subgroup in the majority of studies. Case-fatality rates ranged from 0% to 2·6% in population-based studies and from 0% to 21% in facility-based studies. This review highlights the large gaps in data on the burden ofShigellainfections for low human development index countries and, more specifically, for sub-Saharan Africa.