bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Challenge of asthma in adolescence
Authors: de Benedictis Diletta , Bush Andrew 
Published: June 2007

AbstractThe adolescents with asthma are a distinct group of patients with different problems and needs compared to children and adults. Specific issues of asthma in adolescence are the variability of the clinical spectrum, the presence of particular risk factors for the persistence of symptoms, underdiagnosis and undertreatment of the disease. Refusal of the sick role, denial of symptoms, carelessness about dangerous inhalation exposure, erratic self‐medication, overexertion without taking precautions against exercise‐induced asthma, and a poor relationship between patients, their families, and often doctors are the main obstacles to successful management of asthma in this critical age. There are also major problems of compliance for these patients. The goal of optimal quality of life will be achieved only if the physician thoroughly understands the adolescent's needs and provides optimal care. Pediatr Pulmonol. 2007, 42:683–692. © 2007 Wiley‐Liss, Inc.
New method for the determination of the defect profile in thin layers grown over a substrate
Authors: Zubiaga A. , García J. A. , Plazaola F. , Tuomisto F. , Zúñiga J. , Muñoz‐Sanjosé V. 
Published: June 2007

AbstractWe present a new method to obtain information about the defect profile of films grown over high quality substrates. The method is valid, at least, for films where the positron mean‐diffusion length is small. We have used the method for the case of ZnO films grown over sapphire, but the method can be generalized very easily to other film/substrate systems. Applying the method to the ratio of W and S parameters obtained from Doppler broadening measurements, W/S plots, one can determine the thickness of the film and the defect profile trend in the film, when mainly one positron trap is contributing to positron trapping within the film. Indeed, the quality of such a characterization is very important for the potential technological applications of the film. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Many body effects seen in the positron annihilation experiment
Authors: Kontrym‐Sznajd G. , Sormann H. 
Published: June 2007

AbstractThe electron‐positron (e‐p) momentum density in p‐space for copper, magnesium, cadmium and yttrium, calculated by using various theoretical approaches, are compared with corresponding densities reconstructed from two‐dimensional angular correlation of annihilation radiation (2D ACAR) experimental spectra. We demonstrate that (at least for positrons in metals) strong electron‐electron (e‐e) correlations are clearly visible not only in the Compton scattering but also in positron annihilation experiments. Moreover, a proper description of e‐p correlations needs to include the lattice‐periodical crystal potential. In case of strong lattice effects, the increase of the e‐p enhancement with increasing momentum ‐ the so‐called Kahana‐like enhancement, is vanishing. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Defect studies of hydrogen loaded Nb: bulk metals and thin films
Authors: Čížek J. , Procházka I. , Daniš S. , Melikhova O. , Vlach M. , Žaludová N. , Brauer G. , Anwand W. , Mücklich A. , Gemma R. , Nikitin E. , Kirchheim R. , Pundt A. 
Published: June 2007

AbstractMicrostructure investigations of Nb loaded with H are presented in this work. The microstructure was examined by positron annihilation spectroscopy (PAS), combined with X‐ray diffraction (XRD) and transmission electron microscopy (TEM). The behaviour of H‐loaded bulk samples and thin films was compared. First, the microstructure of the virgin (H‐free) specimens was characterized. Subsequently, the development of the microstructure during step‐by‐step electrochemical H charging was studied. The investigations were performed mainly in the low H concentration region (α‐phase), where the Nb‐H system represents a single phase interstitial solid solution. In bulk samples it was found that new vacancy‐like defects are introduced by H loading. Vacancies surrounded by H were detected also in the electron irradiated bulk samples. Nanocrystalline thin films were produced by sputtering at room temperature. They exhibit a significant volume fraction of grain boundaries with open volume defects which trap H. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
2D‐ACAR studies on microstructure characteristics of porous silicon
Authors: Sivaji K. , Sundar C. S. , Amarendara G. , Rajaraman R. , Padma G. , Sankar S. 
Published: June 2007

AbstractTwo dimensional electron momentum distributions (EMD) have been mapped by the two‐dimensional angular correlation of positron annihilation radiation (2D‐ACAR) to study the electronic structure and microstructural characteristics of porous silicon. The open volume defects associated with vacancies and their complexes present in the porous layer have been analysed using the EMD spectra. Also, the correlation between EMD and the pore formation mechanism was studied and the surface properties were analyzed along with the photoluminescence spectra. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Reactions of free positrons in low temperature polyethylene: delayed Ps formation and positron localization
Authors: Hirade T. , Suzuki N. , Saito F. , Hyodo T. 
Published: June 2007

AbstractPositronium (Ps) can be formed by a reaction of trapped electrons and free positrons at low temperatures in molecular solids. While Ps formation by Ore and spur process must be fast, Ps formation by trapped electrons and free positrons is possible even at later positron age. The evidence of this delayed Ps formation was obtained by age‐momentum correlation measurement of electron‐positron pair annihilation γ‐rays. In this work the S (t) parameter curves measured with trapped electrons and no trapped electrons in polyethylene are interpreted by introducing possible positron reactions. It is quite natural to believe that the delayed Ps formation competes with the positron localization. We have successfully obtained a good simultaneous fit to the observed time dependent S‐parameter curves, S (t), with and without the trapped electrons in the sample. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of the time resolution of a pulsed positron beam
Authors: Reurings Floris , Laakso Antti 
Published: June 2007

AbstractWe analyze the time resolution of the Helsinki pulsed positron beam. The multiple pulsing stages in the beam lead to a non‐trivial pulse shape, which must be taken into account in the subsequent analysis of the data. We study the performance of the pulsing stages and derive an expression for the resolution function, and find a good agreement with the measured spectrum. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Silicon and carbon vacancies in silicon carbide studied by coincidence Doppler broadening spectroscopy
Authors: Zhang J. D. , Cheng C. C. , Ling C. C. , Beling C. D. , Fung S. 
Published: June 2007

AbstractDeconvoluted Coincidence Doppler Broadening Spectroscopy (CDBS) measurements have been made on 300 keV and 1.7 MeV electron irradiated SiC. The lower energy irradiation produces only carbon vacancies while the higher energy produces both carbon and silicon vacancies. This distinction is easily seen in the high (20‐35 mrad) momentum range where a clear atomic signal of Si is seen for the carbon vacancy. In addition to the higher momentum region the higher resolution of the deconvoluted CDBS spectra show structural information relating to the crystal lattice. The autocorrelation function obtained for positrons trapped at carbon vacancies is found to show a stronger lattice signal indicative of a more extended positron wave function and a less strongly bound state. Conversely that positron trapped at the silicon vacancy shows a more damped autocorrelation function characteristic of a more spatially confined positron state. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Subsurface zones in magnesium detected by variable energy positron beam
Authors: Dryzek J. , Schut H. , Dryzek E. 
Published: June 2007

AbstractIn the paper we present positron annihilation studies of the subsurface zones created below pure magnesium surface exposed to sliding. We used the conventional positron techniques i.e. positron lifetime spectroscopy and DSIP (Depth Scanning of the positron Implantation Profile) method, and variable positron energy beam technique. The obtained results suggest the creation of dislocations zone during dry sliding in the subsurface which weakly localize positrons. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Characterization of sonochemically synthesized Au‐Pd nanoparticles by using slow positron beam
Authors: Hori F. , Kojima T. , Tanaka S. , Akita T. , Iwai T. , Onitsuka T. , Taguchi N. , Iwase A. 
Published: June 2007

AbstractBinary AuPd nanoparticles were prepared by sonochemical reduction of solutions containing Au3+, Pd2+ ions and surfactant (SDS: sodium dodecyl sulfate and PEG‐MS: polyethylene glycol monostearate). When using SDS as an additive, AuPd nanoparticles became a core‐shell structure of Au core and Pd shell. AuPd nanoparticle with core‐shell structure has catalytic activity superior to alloyed particle or Pd nanoparticles. In order to study the electronic states of AuPd nanoparticles, positron annihilation Doppler broadening measurements by using slow positron beam (energy range of 0.1 to 10 keV) have been performed for AuPd nanoparticles. The size and shape of the nanoparticles are also examined by using transmission electron microscope (TEM). The differences of Doppler broadening parameters between core‐shell, alloyed AuPd, pure Au and Pd particles were found. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of ceramic nanoparticles on grain growth in ultra fine grained copper prepared by high pressure torsion
Authors: Čížek J. , Procházka I. , Cieslar M. , Kužel R. , Matěj Z. , Cherkaska V. , Islamgaliev R. K. , Kulyasova O. 
Published: June 2007

AbstractBulk ultra‐fine grained (UFG) materials with no residual porosity can be produced by high pressure torsion (HPT). A number of UFG metals exhibit improved mechanical properties consisting in a favourable combination of very high strength and a reasonable ductility. Unfortunately, the thermal stability of UFG structure is rather low. Recrystallization takes place at elevated temperatures and the superior mechanical properties are lost. Thus, it is highly desirable to improve the thermal stability of UFG structure. In the present work we studied the thermal stability of UFG Cu containing Al2O3 nanoparticles. The aim of this work was to check whether the ceramic nanoparticles can inhibit grain growth and, thereby, to extend the thermal stability of UFG structure. We have found that the HPT deformed samples exhibit UFG structure with grain size around 150 nm and a high density of dislocations situated mainly in distorted layers along grain boundaries. The grain growth in the samples which contain 0.5 wt.% of the Al2O3 nanoparticles is shifted to a significantly higher temperatures compared to the pure UFG Cu. Thus, we can conclude that the addition of the Al2O3 nanoparticles (concentration at least 0.5 wt.%) leads to a significant improvement of the thermal stability of UFG structure. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Temperature dependence study of positronium formation in high density polyethylene by positron annihilation lifetime spectroscopy
Authors: Nahid F. , Beling C. D. , Fung S. 
Published: June 2007

AbstractPositron annihilation lifetime spectroscopy has been used to study the formation of positronium in high density polyethylene as a function of temperature over the range 30 K‐350 K. It is observed that the thermal history of the sample, while having no influence on the positronium lifetime, has a strong effect on the formation of positronium. A hysteresis is seen in the positronium formation probability in cooling and heating cycles. This is explained on a two channel formation model, the first channel being through “blob” formation and the second through the pick‐up of shallow trapped electrons. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Doppler broadening of positron annihilation radiation as a probe for the anisotropy of free‐volume‐holes in polymers
Authors: Palacio C. A. , Djourelov N. , Kuriplach J. , Dauwe C. , Laforest N. , Segers D. 
Published: June 2007

AbstractDoppler broadening of annihilation radiation (DBAR) measurements have been performed in uniaxially hot‐drawn poly(methylmethacrylate) (PMMA) samples. The DBAR spectra were deconvoluted into three Gaussians. The full width at half‐maximum of the narrow component which is due to para‐Positronium (p‐Ps) self‐annihilation is under discussion. An anisotropy of the free volume holes (FVHs) has been detected by measuring the deformed samples at the stretching and transverse directions. The sample deformed at 280% was also measured as a function of the orientation angle (0°–90°) with respect to the stretching direction. The momentum distribution of p‐Ps, which is considered as a structureless particle confined in FVH of ellipsoidal or cuboid shape, was calculated as a function of the potential well size and depth and compared with experiment. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effect of cross‐linking on the free volume properties of natural rubber
Authors: Jobando V. O. , Quarles C. A. 
Published: June 2007

AbstractWe used Positron Annihilation Lifetime Spectroscopy (PALS) to investigate the effect of cross‐linking on the free volume properties of Natural Rubber (NR) composites. In order to form any meaningful product for industrial purposes, NR is mixed with different compounds, then cured in a process called vulcanization. One of the most important compounds used in the mixing process is sulfur. Sulfur forms cross‐links with NR restricting the mobility of the polymer chains. Addition of sulfur and vulcanization reduce the o‐Ps lifetime and intensity. By compating un‐vulcanized and vulcanized samples we show that sulfur inhibits Ps formation and that with cross‐link formation during vulcanization the o‐Ps lifetime and intensity both decrease with increasing sulfur concentration. Swelling measurements were also done using toluene absorption to measure cross–link density as a function of sulfur concentration. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Positron lifetime studies on the free volume changes during curing of rubber‐carbon black composites
Authors: Jobando V. O. , Quarles C. A. 
Published: June 2007

AbstractThe free volume behavior as a function of time during curing of natural rubber‐carbon black composites studied by positron annihilation lifetime spectroscopy (PALS) is reported. The lifetime and intensity of the ortho‐positronium (o‐Ps) pick‐off annihilation, which correlate with the average size and the number of holes respectively, were measured as a function of curing time. The samples were cured at 160 °C, while all PALS measurements were made at room temperature. Results for curing D706 (Duradene‐706), a synthetic rubber is also reported and compared with those found from natural rubber (NR). (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Positron spectroscopy of high‐k dielectric films on SiC
Authors: Coleman P. G. , Burrows C. P. , Mahapatra R. , Wright N. G. 
Published: June 2007

AbstractA correlation has been observed between the structural integrity and growth temperature of ∼80 nm‐thick TiO2 films grown on SiO2/4H‐SiC substrates as high‐k dielectric stacks for power device applications, using variable‐energy positron annihilation spectroscopy. The structural change, tentatively attributed to a decrease in oxygen vacancy concentration, was observed as the TiO2 growth temperature was increased in the range 700 to 1000 °C, whereas grain boundaries form in the polycrystalline material grown at the highest temperatures. It is proposed that the optimal electrical performance for films grown at 800 °C reflects a balance between decreasing vacancy concentration and increasing grain boundary formation. Because positrons are swept to the SiO2/SiC interface by a field in the substrate, VEPAS is strongly sensitive to interface states, which can have important consequences for channel mobility and thus the electrical performance of the devices. The use of a number of lineshape parameters (beyond the standard S and W) has been applied to these measurements, enabling clearer insights to be gained. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Doppler broadening of annihilation radiation spectroscopy study using Richardson‐Lucy, Maximum Entropy and Huber methods
Authors: Yu D. P. , Zhang J. D. , Cheng V. , Beling C. D. , Fung S. 
Published: June 2007

AbstractThe Richardson‐Lucy, Maximum Entropy and Huber regularization methods are popularly used in solving ill‐posed inverse problems. This paper considers the use of these three methods in the deconvoluting DBARS (Doppler Broadening of Annihilation Radiation Spectroscopy) data. As DBARS data have a constant background on the high‐energy side and a long exponential tail on the low‐energy side, we check the different deconvolution schemes paying specific attention to the quality of the deconvolution at the peak and tail positions. Comparison of the three methods is made by testing on Monte‐Carlo simulated data both in terms of the deconvoluted quality and computational resources required. Finally, we apply these methods to experimental DBARS data taken on polycrystalline metal samples. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Quantitative precipitation forecasting in the Alps: The advances achieved by the Mesoscale Alpine Programme
Authors: Richard Evelyne , Buzzi Andrea , Zängl Günther 
Published: June 2007

AbstractThe improvement of Quantitative Precipitation Forecasting (QPF) in mountainous regions was a major supporting objective of the Mesoscale Alpine Programme (MAP) project P1 devoted to the study of orographic precipitation. This paper reviews the main MAP‐related achievements regarding QPF improvement and highlights the MAP impact on developing QPF research and planning future operational strategies. Recent results based on MAP case‐studies, on data analysis and assimilation, on quantification of model uncertainties, and on model intercomparison and verification substantiate the progress made in recent years in improving model performance in relation to short‐range, high‐resolution forecasting in complex topography regions, well represented by the European Alps. Copyright © 2007 Royal Meteorological Society
Gravity waves above a convective boundary layer: A comparison between wind‐profiler observations and numerical simulations
Authors: Böhme T. , Lane T. P. , Hall W. D. , Hauf T. 
Published: June 2007

AbstractWind‐profiler observations and three‐dimensional numerical modelling are used to investigate gravity waves generated over convectively active boundary layers on 12 and 13 May 2001 at Lindenberg, Germany. The results illustrate the importance of changes in the background wind and stability profile in influencing the vertical propagation of the gravity waves. The resultant changes in vertical propagation cause the dominance of relatively long‐wavelength, long‐period waves at high levels and the dominance of relatively short‐wavelength, short‐period waves near the top of the convective boundary layer. There are important differences between the two days in the wave‐propagation characteristics, due to subtle changes in the background flow conditions. Copyright © 2007 Royal Meteorological Society
Data assimilation in the FOAM operational short‐range ocean forecasting system: a description of the scheme and its impact
Authors: Martin M. J. , Hines A. , Bell M. J. 
Published: June 2007

AbstractA detailed description of the data assimilation scheme used in the Forecasting Ocean Assimilation Model (FOAM) operational ocean forecasting system is presented. The theoretical basis for the scheme is an improved version of the analysis correction scheme, which includes information from previously assimilated data. The scheme requires the a priori specification of error covariance information for the background model field and the observations. The way in which these error covariances have been estimated is described and some examples are given. The FOAM system assimilates sea surface temperature, sea‐level anomaly, temperature profile, salinity profile and sea‐ice concentration data. Aspects of the scheme that are specific to each of these observation types are described.Two sets of experiments demonstrating the impact of the data assimilation are presented. The first set are in an idealized identical‐twin setting, using the ${1}\over{9}$° ‐resolution North Atlantic FOAM configuration in which the state of the true ocean is assumed to be known. These experiments show that the analyses and forecasts are improved by assimilating the altimeter sea‐level‐anomaly data. The second set of experiments comprise data impact studies in a realistic hindcast setting. These experiments show a positive impact on the analyses from the Argo temperature‐ and salinity‐profile data. Copyright © 2007 Royal Meteorological Society
Controlling correlated processes of Poisson counts
Authors: Weiß Christian H. 
Published: June 2007

AbstractThe class of INARMA models is well suited to model the autocorrelation structure of processes with Poisson marginals arising in context of statistical quality control. After reviewing briefly the basic principles and important members of this broad family of models, we concentrate on the INAR(1) model, which is of particular relevance for quality control. We suggest four approaches to control such count processes, and compare their run length performance in a simulation study. Results show that only some of the out‐of‐control situations considered can be controlled effectively with the discussed control schemes. Copyright © 2007 John Wiley & Sons, Ltd.
On the Empirical Bayes approach to the problem of multiple testing
Authors: Bogdan Małgorzata , Ghosh Jayanta K. , Ochman Aleksandra , Tokdar Surya T. 
Published: June 2007

AbstractWe discuss the Empirical Bayes approach to the problem of multiple testing and compare it with a very popular frequentist method of Benjamini and Hochberg aimed at controlling the false discovery rate. Our main focus is the ‘sparse mixture’ case, when only a small proportion of tested hypotheses is expected to be false. The specific parametric model we consider is motivated by the application to detecting genes responsible for quantitative traits, but it can be used in a variety of other applications. We define some Parametric
Empirical Bayes procedures for multiple testing and compare them with the Benjamini and Hochberg method using computer simulations. We explain some similarities between these two approaches by placing them within the same framework of threshold tests with estimated critical values. Copyright © 2007 John Wiley & Sons, Ltd.
Cospas–Sarsat LEO and GEO: Satellite distress and safety systems (SDSS)
Authors: Ilcev D. S. 
Published: June 2007

AbstractCospas–Sarsat Low Earth Orbit (LEO) and Geostationary Earth Orbit (GEO) networks must provide enhanced service of Satellite Distress and Safety Systems (SDSS); to improve Search and Rescue (SAR) operations in all environments; and to increase safety and security at low cost for numbers of mobiles at sea, on land and in the air. This paper describes the concepts of integrated LEO and GEO space configurations in function of Cospas (space system for search of distress vessels and airplanes) and Sarsat SDSS, and SAR infrastructures. The paper also reviews satellite repeaters providing SDSS service for satellite beacons known as an Emergency Position Indicating Radio Beacons for Maritime, Personal Locator Beacons for land (road and rail), and Emergency Locator Transmitter (ELT) for aeronautical applications. Copyright © 2007 John Wiley & Sons, Ltd.