bluuebunny/crossref_metadata_2025_split huggingface dataset:
Design of a liquidless superconducting accelerator for positron annihilation lifetime spectroscopy
Authors: Oshima N. , Kuroda R. , He C. , Kinomura A. , Ohdaira T. , Toyokawa H. , Suzuki R. , Hayashizaki N. , Hattori T. 
Published: June 2007

AbstractA design of a superconducting accelerator for a pulsed positron beam of ∼1 MeV for positron annihilation lifetime spectroscopy is proposed. The total system can be extremely small with an application of superconducting technology. Both a miniaturization and easy maintenance of the accelerator can be achieved by usage of a small liquidless refrigerator for cooling of a superconducting RF cavity. Moreover, the operation duty cycle of the superconducting cavity is ∼100% which is much larger than that of a normal conducting one. The required RF power to drive the system is ∼10 W, therefore a large‐size klystron is not necessary. The designed system including a slow positron source is small (∼2 m3) enough to be used in a general laboratory. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Vacancy‐solute association in coherent nanostructures formed in a commercial Al‐Zn‐Mg‐Cu alloy
Authors: Dupasquier A. , Ferragut R. , Iglesias M. M. , Quasso F. 
Published: June 2007

AbstractThe role of vacancy‐solute association in the formation of coherent precipitates at room temperature (RT) and at 70 °C was studied by means of coincidence Doppler broadening (CDB) spectroscopy. The formation of clusters and GP zones was monitored by differential scanning calorimetry (DSC). Two conditions were explored at low temperature: a) one‐step aging after solution treatment and quenching and b) secondary aging (after solution treatment and quenching + 5 days at RT + 8 min at 150°C). The assessment of the average fractional concentration of solute in contact with the vacancies was obtained by analyzing the CDB data. The results show considerable aggregation of Cu to vacancies at the very early stage of decomposition of the supersaturated solid solution; the contribution of Zn and Mg increases progressively with the formation of coherent precipitates. The preliminary exposure at 150 °C does not alter this sequence, although a reduction in the dissolution enthalpy observed during DSC scans shows retarded formation of coherent precipitates. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Identification of lattice defects in Cu thin films by positron annihilation spectroscopy
Authors: Mizuno Masataka , Kihara Teruo , Araki Hideki , Shirai Yasuharu , Onishi Takashi 
Published: June 2007

AbstractPositron lifetime measurements have been performed for Cu thin films in order to identify lattice defects. Theoretical positron lifetimes of vacancy clusters of Cu are also calculated for identification of the experimental values. Cu thin films were prepared by electro chemical deposition (ECD) and physical vapour deposition (PVD). All of the Cu thin films have longer positron lifetimes than bulk Cu does. This indicates that lattice defects are introduced during deposition. However composition analysis of positron lifetimes shows that whereas vacancy clusters exist in the ECD‐Cu thin film, the positron lifetime of defect component in the PVD‐Cu thin films is shorter than that of mono‐vacancy. On the other hand, the positron lifetime of mono‐vacancy was detected in PVD‐Cu‐0.5 at%Sb thin film prepared by PVD. In order to elucidate the effect of Sb, first‐principles calculations have been performed for Cu including Sb and mono‐vacancy. The result suggests that mono‐vacancies are introduced because of the binding energy between a Sb atom and mono‐vacancy. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Microstructure investigations of ultra‐fine grained Mg‐Gd alloys prepared by high pressure torsion
Authors: Čížek J. , Procházka I. , Smola B. , Stulíková I. , Kužel R. , Matěj Z. , Cherkaska V. , Islamgaliev R. K. , Kulyasova O. 
Published: June 2007

AbstractMg‐Gd represents a promising light hardenable alloy with a high creep resistance even at elevated temperatures. A disadvantage of this alloy consists in a low ductility. Recently it has been demonstrated that ultra fine grained (UFG) metals with grain size around 100 nm can be produced by high pressure torsion (HPT). A number of UFG metals exhibit favourable mechanical properties consisting in a combination of a very high strength and a significant ductility. The HPT processing creates a high density of defects, especially dislocations, in UFG material. These defects play key role in the specific physical properties of UFG materials. Defects studies of UFG materials are, therefore, very important for understanding of their unusual properties. Positron lifetime (PL) spectroscopy is one of the most powerful techniques for investigations of open‐volume defects. In the present work we employed PL spectroscopy for defect studies of UFG Mg‐Gd alloys prepared by HPT. The PL investigations were combined with transmission electron microscopy, X‐ray diffraction, and microhardness measurements. At first, the microstructure of the as‐deformed specimens was characterized. Subsequently, the specimens were isochronally annealed and the development of microstructure with increasing temperature was investigated. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High‐resolution reconstruction of a tracer dispersion event: application to ETEX
Authors: Bocquet Marc 
Published: June 2007

AbstractIn a previous two‐part paper, new methods for reconstructing the source of an atmospheric tracer at regional scale were developed. Specifically, the ‘maximum entropy on the mean’ (MEM) method was extended to large (though linear) data assimilation problems. Tests using twin experiments and a limited subset of the data from the European Tracer Experiment (ETEX) were performed. Although temporal reconstruction knowing the location of the source was satisfying, a full three‐dimensional reconstruction with real data was still out of reach.In this paper, using the MEM method and some of its refinements, a reconstruction using all ETEX‐I measurements at a resolution of 1.125 × 1.125 × 1 h is shown to be possible. This allows for a reconstruction of the full dispersion event. The MEM retrieval of the tracer plume using what is believed to be a good prior is then compared to retrievals using other priors, including Gaussian priors. Eventually, a reconstruction using all data sequentially in time (rather than all together) is obtained. This helps define what a maximum‐entropy filter applied to sequential data assimilation of a linear tracer should be able to do, with a view to an efficient emergency response in case of an accidental release of pollutant. Copyright © 2007 Royal Meteorological Society
Gap flows: Results from the Mesoscale Alpine Programme
Authors: Mayr Georg J. , Armi Laurence , Gohm Alexander , Zängl Günther , Durran Dale R. , Flamant Cyrille , Gaberšek Saša , Mobbs Stephen , Ross Andrew , Weissmann Martin 
Published: June 2007

AbstractAn overview of advances in the observation, modelling, forecasting, and understanding of flows through gaps achieved in the Mesoscale Alpine Programme is given. Gaps are lateral constrictions of topography (level gaps) often combined with vertical terrain changes (passes). Of the possible flow configurations, only an asymmetric one (relatively deep and slow upstream, accelerating and thinning downstream), which connects two different ‘reservoirs’ on each side of the gap, is examined. The flow is strongly nonlinear, making hydraulics (reduced‐gravity shallow‐water theory) rather than linear theory the simplest conceptual model to describe gap flow. Results from idealized topographical and flow conditions are presented, together with gap flows through a pass in the central Alpine Wipp Valley. For a given depth of the upstream reservoir, the gap controls the mass flux through it and marks the transition from a subcritical flow state upstream to a supercritical one downstream, which eventually adjusts to the downstream ‘reservoir’ in a hydraulic jump. Three gap flow prototypes were found: a classical layer one with neutral stratification and a capping inversion and two with a continuous stratification, for which a special analytical self‐similar hydraulic solution exists. In all three cases, a deepening wedge of nearly mixed and stagnant air forms on top of the gap flow plunging down from the pass. The descent causes a warming and (relative) drying of the air, making gap flows a special case of föhn. Topographical variations smaller than the gap scale cause additional hydraulic jumps, flow separation, vorticity banners, gravity waves, and interactions with cold pools. Turbulent friction cannot be neglected. The climatological frequency of gap flows depends on the establishment of two different reservoirs and reaches 20% for the Wipp Valley. Copyright © 2007 Royal Meteorological Society
Lessons on orographic precipitation from the Mesoscale Alpine Programme
Authors: Rotunno Richard , Houze Robert A. 
Published: June 2007

AbstractAlthough moisture‐laden airflow towards a mountain is a necessary ingredient, the results from the Mesoscale Alpine Programme (MAP) demonstrate that detailed knowledge of the orographically modified flow is crucial for predicting the intensity, location and duration of orographic precipitation. Understanding the orographically modified flow as it occurs in the Alps is difficult since it depends on the static stability of the flow at low levels, which is heavily influenced by synoptic conditions, the complex effects of latent heating, and the mountain shape, which has important and complicated variations on scales ranging from a few to hundreds of kilometres. Central themes in all of the precipitation‐related MAP studies are the ways in which the complex Alpine orography influences the moist, stratified airflow to produce the observed precipitation patterns, by determining the location and rate of upward air motion and triggering fine‐scale motions and microphysical processes that locally enhance the growth and fallout of precipitation. In this paper we review the major findings from the MAP observations and describe some new research directions that have been stimulated by MAP results. Copyright © 2007 Royal Meteorological Society
Upper‐tropospheric flow features and the Alps: An overview
Authors: Hoinka Klaus P. , Davies Huw C. 
Published: June 2007

AbstractOne focus of the Mesoscale Alpine Programme (MAP) was the study of upper‐tropospheric potential vorticity (PV) anomalies that take the form of narrow meridionally elongated troughs termed ‘PV streamers’. A systematic effort was undertaken within the MAP framework to: establish a streamer climatology, develop appropriate instrumentation and undertake a measurement programme to better ascertain their structure, study both their intrinsic dynamics and their modification by the Alps, and perform model experiments to examine their significance for numerical weather prediction.Here an overview is given of the progress made toward achieving these objectives. In particular it is shown that PV streamers translating toward the Alpine region are dynamically distinctive and constitute an identifiable precursor of and contribute seminally to heavy precipitation events on the south side of the Alps and possess rich mesoscale sub‐structures that can be examined with novel water vapour absorption lidar instrumentation. It is also shown that the accurate representation of a streamer might well be a critical prerequisite for accurate quantitative prediction of mesoscale precipitation. Copyright © 2007 Royal Meteorological Society
Turbulent flows on forested hilly terrain: the recirculation region
Authors: Poggi D. , Katul G. G. 
Published: June 2007

AbstractA number of analytical and numerical studies employing first‐order closure principles have suggested that canopy flows on gentle sinusoidal hills feature a recirculation region, situated on the lee side, that can dramatically affect scalar transfer between the biosphere and the atmosphere. To date, the onset of this region, and its effects on bulk flow properties, have not been experimentally investigated. We study the applicability of first‐order closure schemes jointly with the properties of this recirculation region, using detailed laser Doppler anemometry (LDA) measurements. These experiments are conducted in a neutrally stratified boundary‐layer flow within a large flume over a train of gentle and narrow hills. The canopy is composed of an array of vertical cylinders with a frontal‐area index concentrated in the upper third, to resemble a tall hardwood forest at maximum leaf area. The LDA measurements are recorded for both sparse and dense canopies. We find that, while the onset of a recirculation region is ambiguous in the sparse‐canopy case, it is well delineated in the dense‐canopy case. This finding constitutes the first experimental evidence confirming the analytical and numerical model predictions concerning this region in dense canopies on gentle hills. Moreover, we show that the presence of the recirculation region can explain the anomalous pressure variation across the hill (first reported in numerical simulations) using an ‘effective hill shape’ function. Detailed momentum‐flux measurements show, surprisingly, that the effective mixing length leff within the canopy and in the inner layer is not significantly affected by the recirculation region. We expected leff to be comparable to the size of the vortex responsible for the recirculation zone, but the measurements show that leff maintains its canonical canopy turbulence shape. Using laser‐induced fluorescence (LIF) measurements, we find that the recirculation region is not characterized by a classical ‘rotor’, but by a highly intermittent zone with alternating positive and negative velocity values in the lower layers of the canopy. These LIF measurements may explain why leff maintains its canonical canopy turbulence shape in the recirculation region. The LIF measurements also show that the main mechanism for scalar transfer within the recirculation region is a sequence of accumulation–ejection episodes that are quasi‐periodic in nature. Copyright © 2007 Royal Meteorological Society
Restricted randomization and multiple responses in industrial experiments
Authors: Bjerke Frøydis , Langsrud Øyvind , Aastveit Are Halvor 
Published: June 2007

AbstractTwo issues regarding designed experiments are discussed; restrictions on randomization and multiple responses. The former is typically related to hard‐to‐vary factors and factors appearing in separate stages of a process experiment. Randomization restrictions should be taken into account in the construction of the design as well as in the statistical modelling. In the paper, a case study of sausage production is discussed, having a split‐plot model with correlated multiple responses. Multiple responses are handled in two ways, by principal component analysis (PCA) followed by ANOVA of the principal components, and by a newly developed alternative, the ‘50–50 MANOVA’. Multiple tests of correlated response variables are also described. Practical aspects of the planning, performing, response measurements, and statistical analysis are emphasized throughout. Hence, the paper aims to extend the utility of statistical methods in industry by linking design of experiments to multivariate analysis of the responses. Copyright © 2007 John Wiley & Sons, Ltd.
Simultaneous analysis of multiple bioactive constituents in Rheum tanguticum Maxim. ex Balf. by high‐performance liquid chromatography coupled to tandem mass spectrometry
Authors: Jin Wei , Wang Ying‐Feng , Ge Ri‐Li , Shi Hai‐Ming , Jia Cun‐Qin , Tu Peng‐Fei 
Published: June 2007

AbstractA simple, rapid method was developed using on‐line high‐performance liquid chromatography (HPLC)–diode array detection (DAD)/electrospray ionization mass spectrometry (ESI‐MS) to simultaneously analyze multiple bioactive constituents in the extract of Rheum tanguticum Maxim. ex Balf. (Dahuang), a traditional Chinese medicine (TCM). Many bioactive constituents gave prominent [MH]− ions in the negative ion ESI mass spectra. Among them, 41 different constituents including 16 anthraquinone derivatives, 7 phenylbutanone glucopyranosides, 4 stilbenes and 14 tannins were unambiguously identified or tentatively characterized based on their retention times, UV spectra and mass spectra in comparison with the data from standards or references. Meanwhile, some principles of fragmentation behavior for different types of constituents were proposed, which could contribute to the elucidation of these constituents in Rheum tanguticum. Copyright © 2007 John Wiley & Sons, Ltd.
Membrane proteome in Escherichia coli probed by MS3 mass spectrometry: a preliminary report
Authors: Cirulli Claudia , Marino Gennaro , Amoresano Angela 
Published: June 2007

AbstractCharacterization of the membrane proteome is particularly intriguing since a better knowledge in this field might lead to new insights into the function of different membrane systems. Despite the biological relevance of surface proteins however, their characterization still remains a challenging task. Outer membrane proteins (OMPs) of Gram‐negative bacteria are key molecules that interface the cell with the environment. Hence, surface proteins of Gram‐negative bacteria contain proteins that might be good targets for drugs, antimicrobials or detection systems and they may become components of effective vaccines. In this respect, Escherichia coli has been chosen as a model organism for several structural and functional studies aimed at understanding the biophysical and biochemical organization of proteins in Gram‐negative cell walls. Here we present first results for the identification of bacterial surface exposed proteins in E. coli K12 based on the use of dansyl chloride labelling coupled with bidimensional tandem mass spectrometry exploiting the advantage of precursor ion/MS3 scan modes. This procedure resulted in a promising, simple, and rapid strategy for the identification of membrane proteins in E. coli as model organism, thus avoiding time‐consuming procedures based on two‐dimensional liquid chromatography and electrophoresis. The proteins identified could be grouped into five major families: outer membrane (29 proteins), lipoproteins (6 proteins), transmembrane (43 proteins) families. Copyright © 2007 John Wiley & Sons, Ltd.
Boundedness in Lurie system with stiffening nonlinearities
Authors: Ben Abdallah Abdallah , Hammami Mohamed Ali 
Published: June 2007

AbstractIn this paper, we deal with the problem of boundedness of solutions in single‐input single‐output Lurie system. We prove the boundedness of solutions from the stability of zero dynamics under a restriction on the nonlinearity. The linear block is supposed to be of relative degree one or two, stabilizable by high‐gain output feedback and not necessary minimum phase. The nonlinearity is required to have the stiffening property. Copyright © 2007 John Wiley & Sons, Ltd.
Cluster without fluster: The effect of correlated outcomes on inference in randomized clinical trials
Authors: Proschan Michael , Follmann Dean 
Published: June 2007

AbstractInference for randomized clinical trials is generally based on the assumption that outcomes are independently and identically distributed under the null hypothesis. In some trials, particularly in infectious disease, outcomes may be correlated. This may be known in advance (e.g. allowing randomization of family members) or completely unplanned (e.g. sexual sharing among randomized participants). There is particular concern when the form of the correlation is essentially unknowable, in which case we cannot take advantage of the correlation to construct a more efficient test. Instead, we can only investigate the impact of potential correlation on the independent‐samples test statistic. Randomization tends to balance out treatment and control assignments within clusters, so it is logical that performance of tests averaged over all possible randomization assignments would be essentially unaffected by arbitrary correlation. We confirm this intuition by showing that a permutation test controls the type 1 error rate in a certain average
sense whenever the clustering is independent of treatment assignment. It is nonetheless possible to obtain a ‘bad’ randomization such that members of a cluster tend to be assigned to the same treatment. Conditioned on such a bad randomization, the type 1 error rate is increased. Published in 2007 by John Wiley & Sons, Ltd.
Field tests of wind turbines submitted to real voltage dips under the new Spanish grid code requirements
Authors: Gómez E. , Fuentes J. A. , Molina‐García A. , Ruz F. , Jiménez F. 
Published: June 2007

AbstractThis paper adds the new Spanish grid code to the previously published works about the comparison of international regulations for connection of wind turbines to the network. All the electrical magnitudes—currents and active and reactive power—regulated in the Spanish grid code are studied when the wind turbines are submitted to real voltage dips. Because grid codes and, specifically, the Spanish grid code do not fix the reactive power definition to be applied, four definitions commonly used have also been studied. Taking advantage of the voltage dips field tests carried out to the Gamesa G80 wind turbines, the results obtained for two representative voltage dip tests are presented: a three‐phase and a phase‐to‐phase voltage dip. Copyright © 2007 John Wiley & Sons, Ltd.
Estimating seasonal density of blue sheep (Pseudois nayaur) in the Helan Mountain region using distance sampling methods
Authors: Liu Zhensheng , Wang Xiaoming , Teng Liwei , Cui Duoying , Li Xinqing 
Published: June 2007

AbstractThe monitoring of animal populations is necessary to conserve and manage the rare or harvest species and to understand the population change over several years. We used distance sampling methods to estimate seasonal density of blue sheep in a 2,740 km2area of Helan Mountain region by walking along 32 transect lines from winter 2003 to autumn 2005. In all, 367–780 blue sheep were observed in 91–143 groups in the surveys during the seasons. Observed mean group size ranged from 3.42 to 8.35 individuals; encounter rate, the number of groups detected per kilometre, varied from 0.19 to 0.30 during the seasons. A hazard rate key function with cosine series expansion and a half‐normal key function with either cosine or simple polynomial series expansion were the best fitting models based on the lowest value of Akaike's information criterion (AIC). Density estimates varied between 3.627 sheep per square kilometre in spring 2004 and 4.635 per square kilometre in summer 2005. There were no detectable differences in estimated density among seasons (P= 0.887). The estimated density of blue sheep was negatively correlated with the total number of deaths (P< 0.05), number of sub‐adult males’ deaths (P< 0.05), number of sub‐adult females’ deaths (P< 0.05), and number of male lambs’ deaths (P< 0.05). We concluded that distance sampling surveys should be used to monitor long‐term population trends to provide the best quantitative estimates of blue sheep populations in the Helan Mountains region.