bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of quantum‐dots density on average in‐plane strain of optoelectronic devices investigated by high‐resolution X‐ray diffraction
Authors: Freitas Raul O. , Diaz Beatriz , Abramof Eduardo , Quivy Alain A. , Morelhão Sérgio L. 
Published: June 2009

AbstractHigh‐resolution X‐ray diffractometry is used to probe the nature of a diffraction‐peak broadening previously noticed in quantum dots (QDs) systems with freestanding InAs islands on top of GaAs (001) substrates [Freitas et al., Phys. Status Solidi (A) 204, 2548 (2007)]. The procedure is hence extended to further investigate the capping process of InAs/GaAs QDs. A direct correlation is established between QDs growth rates and misorientation of lattice‐planes at the samples surfaces. This effect provides an alternative tool for studying average strain fields on QDs systems in standard triple axis diffractometers running on X‐ray tube sources, which are much more common than synchrotron facilities.
Fourier transform holography in the context of coherent diffraction imaging with hard X‐rays
Authors: Stadler Lorenz‐M. , Gutt Christian , Autenrieth Tina , Leupold Olaf , Rehbein Stefan , Chushkin Yuriy , Grübel Gerhard 
Published: June 2009

AbstractCoherent diffraction imaging (CDI) with 8 keV X‐rays is used to image a gold nanostructure. Experimental details are given and frequently encountered problems such as missing low spatial frequency information and parasitic slit scattering are discussed. As a possible remedy, hard X‐ray Fourier transform holography (FTH) is presented and its robustness with respect to the diffraction pattern quality is demonstrated. It is shown that even with a few‐second exposure to an unfocussed beam, the object structure can be clearly recognised. FTH in combination with CDI is ideal for single‐shot imaging of micron‐sized objects using femtosecond flashes of hard X‐rays at the upcoming free‐electron laser facilities in the USA, Japan and Germany.
Anisotropy of mosaic structure of GaAsP layers grown on GaAs substrates
Authors: Saka T. , Kato T. , Jin X. G. , Tanioku M. , Ujihara T. , Takeda Y. , Yamamoto N. , Nakagawa Y. , Mano A. , Okumi S. , Yamamoto M. , Nakanishi T. , Horinaka H. , Matsuyama T. , Yasue T. , Koshikawa T. 
Published: June 2009

AbstractThe crystalline structure of GaAsP layers grown on GaAs and GaP (001) substrates, used for spin polarized photocathodes, has been investigated by X‐ray diffraction. The layers on the GaAs substrate possess a mosaic structure observable by X‐ray topography and consist of many large blocks. The mosaicity is anisotropic and the distribution of the mosaic is restricted within the (110) plane, and the blocks zigzag around the [110] direction. The layer grown on the GaP substrate was uniform and no mosaic was observed in the topographs. The results indicate that different mechanisms of strain release occur in GaAsP layers for tensile and compressive strains.
Elliptical micropipes in SiC revealed by computer simulating phase contrast images
Authors: Argunova Tatiana , Kohn Victor , Jung Ji‐Won , Je Jung‐Ho 
Published: June 2009

AbstractThe elliptical micropipes in SiC are studied using computer simulation of the phase contrast images. The experimental measurements of “white beam” images are performed at third‐generation synchrotron radiation source in Pohang, Korea. We reveal that the transmitted X‐ray spectrum of a high brilliance with a pronounced maximum at 16 keV enables to form partially coherent images even for transparent objects. The computer simulation allows one to automatically determine the diameters of elliptical cross‐sections based on best matches between calculated and experimental intensity profiles. We show that the micropipes studied here have extended elliptical cross‐sections, sometimes rotating around the micropipe axis.
X‐ray diffraction study of strain and defect structure of nonpolar a‐plane GaN‐layers grown on r‐plane sapphire
Authors: Kyutt R. N. , Shcheglov M. P. , Ratnikov V. V. , Kalmykov A. E. 
Published: June 2009

AbstractStructural state of nonpolar a‐plane GaN layers grown by MOVPE on r‐plane sapphire is investigated by X‐ray diffraction method. Interplanar spacings were measured in three directions and corresponding strains were determined. A crystalline perfection was studied by measurement of diffraction peaks of θ‐ and θ–2θ‐scanning in Bragg‐ and Laue‐diffraction geometry. Their FWHM was analyzed by Williamson–Hall plots. Anisotropy of the elastic strains and the peak broadening was revealed. It is shown that a different broadening of diffraction pattern in two in‐plane directions is not caused by mosaicity and can be explained by a specific distribution of dislocations.
Synchrotron topographic studies of growth defects in the core of a SrLaGaO4 single crystal
Authors: Malinowska Agnieszka , Lefeld‐Sosnowska Maria , Wieteska Krzysztof , Wierzchowski Wojciech , Härtwig Jürgen , Graeff Walter 
Published: June 2009

AbstractSamples cut out from different regions of SrLaGaO4 (SLG) single crystal grown along [001]‐direction were studied with a number of X‐ray diffraction topographic methods exploring both conventional and synchrotron X‐ray sources. The synchrotron investigation included in particular white beam projection transmission topography at ultra short wavelength and taking monochromatic beam topographs at different points of the rocking curves at different azimuths. The methods enabled the evaluation of the character of lattice deformation connected with the characteristic ‘rod‐like’ defects observed in the core region of the crystal. A shrinkage of the material inside the defects was indicated.
Influence of magnetic anisotropy and dipolar interactions on magnetocaloric effect in nanostructured materials
Authors: Prida Victor M. , Vega Victor , Serantes David , Baldomir Daniel , Ilyn Maxim , Zhukov Arcady P. , González Julián , Hernando Blanca 
Published: June 2009

AbstractWe outline the magnetic and magnetocaloric behaviour of magnetic nanoparticles distributed into columnar‐like arrangements with their easy axes collinear aligned along the chain direction, and comparing to that of ferromagnetic nanowires arrays. An extended Monte Carlo model taking into account the influence of both, the magnetic anisotropy and magnetostatic interactions of dipolar origin between ferromagnetic nanoparticles chains, has been developed. The existence of a maximum in thermomagnetic curves for applied magnetic fields up to 2.5 times the anisotropy field value of the system, and the coexistence of positive and negative magnetocaloric effect have been predicted confirming the experimental results found in highly ordered arrays of ferromagnetic nanowires.Positive and negative MCE regimes in an array of single magnetic domain ferromagnetic nanowires and its dependence on the applied field value. The inset shows the MFM image of the magnetic monodomain dipole structure for an isolated Ni‐rich nanowire.magnified image
Comparative studies of Lu3Al5O12:Ce and Y3Al5O12:Ce scintillators for gamma‐ray detection
Authors: Chewpraditkul W. , Swiderski L. , Moszynski M. , Szczesniak T. , Syntfeld‐Kazuch A. , Wanarak C. , Limsuwan P. 
Published: June 2009

AbstractThe performance of Lu3Al5O12:Ce (LuAG:Ce) and Y3Al5O12:Ce (YAG:Ce) scintillators were compared under γ‐ray excitation using photomultiplier tube (PMT) readout. Light yield non‐proportionality and energy resolution were measured with a Photonis XP5500B PMT. The energy resolution, obtained in this work for 662 keV γ‐rays, was 6.7 and 7.0%, respectively, for LuAG:Ce and YAG:Ce detectors. A fast component in the scintillation decay of LuAG:Ce crystal is faster than that of YAG:Ce crystal, whereas the relative intensity of a fast component for YAG:Ce crystal is higher than that of LuAG:Ce crystal. The coincidence time resolution, obtained in this work for 511 keV annihilation quanta, was 583 and 660 ps, respectively, for LuAG:Ce‐ and YAG:Ce‐based detectors in coincidence experiment together with a BaF2 scintillation detector. Normalized coincidence time resolution was also discussed in terms of a number of photoelectrons and decay time of the light pulse.
Growth and electrical properties of AlxGa1−xN/GaN heterostructures with different Al‐content
Authors: Köhler K. , Müller S. , Waltereit P. , Kirste L. , Menner H. P. , Bronner W. , Quay R. 
Published: June 2009

AbstractHigh electron mobility transistor material and device properties based on AlxGa1−xN/GaN heterostructures with an Al‐content ranging from 12 to 35% are presented. The Al‐content of the low pressure metal‐organic vapor‐phase epitaxy grown samples on semi‐insulating SiC and sapphire was measured by high resolution X‐ray diffraction; carrier concentration and mobility by Hall effect. The sheet carrier density in the nominally undoped structures increases with the Al‐content from 3.6 × 1012 to 1.4 × 1013 cm−2 due to spontaneous and piezoelectric polarization. Comparison of the electrical data with a model based on polarization and strain induced effects in dependence of the Al‐composition shows good agreement. Further discussion and presentation on devices is restricted to data on SiC substrates. We quantitatively relate threshold voltage and extrinsic transconductance of FETs to the carrier concentration und thus to the Al‐content in the barrier. Excellent large signal performance is achieved over the AlxGa1−xN‐composition range from 14 to 30%.
Development of nanostructured materials by mechanical alloying and/or rapid solidification
Authors: Bonastre Jordi , Chognon Eddy , Escoda Lluïsa , Güell Josep M. , Hernando Blanca , Suñol Joan Josep 
Published: June 2009

AbstractThe knowledge of thermal behaviour of materials is important in order to control their structure and properties. In nanocrystalline materials obtained from amorphous alloys, the knowledge of the crystallization kinetics permits to design special thermal treatments to develop materials with specific microstructure. The milling of melt‐spun ribbons is a two‐steps procedure to develop new nanostructured materials. Two, Co and Fe rich, melt‐spun alloys were obtained and mechanically alloyed in low energy milling conditions, and their structure and thermal behaviour was analyzed. The thermal study was performed by means of differential scanning calorimetry. All experimental curves are derived from non‐isothermal calorimetric experiments. Good agreement is observed between the transformation curves and the experimental data, which verifies the reliability of the approach and the validity of the rate constant model description. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the stress‐strain curves in gold and aluminum nanowires
Authors: Pastor‐Abia L. , Caturla M. J. , SanFabián E. , Chiappe G. , Louis E. 
Published: June 2009

AbstractThe engineering stress‐strain curves of gold and aluminum nanowires have been investigated by means of Molecular Dynamics. Nanowires were stretched at constant strain rate and a temperature of 4.2 K. Atoms at fixed positions with velocities randomly distributed according to Maxwell distribution were taken as initial conditions.Jumps observed to occur in the stress‐strain curves are associated to atoms that move from the bulk to the surface. Averaging over many realizations allows to conclude that, beyond the yield point, the system does not harden, in line with experimental results. Varying the nanowires shape factor allowed to identify surface effects, crucial in these extremely small systems (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The interior interfaces of a semiconductor/metal nanocomposite and their influence on its physical properties
Authors: Granitzer P. , Rumpf K. , Poelt P. , Albu M. , Chernev B. 
Published: June 2009

AbstractA semiconductor/metal hybrid system with silicon as base material and embedded metal nanostructures is fabricated in two steps by anodizing the silicon substrate in an aqueous hydrofluoric acid solution and a subsequent electrodeposition process. The achieved self‐assembled nanoscopic hybrid system consists of a quasi‐regular 3‐dimensional arrangement of metal nanostructures embedded within the pores of the silicon matrix. The used metals are Ni, Co and their alloys, whereas mainly Ni is considered in the following. In such a hybrid system the interface between metal and silicon nanostructures is of interest in correlation with the properties of the material and can be influenced by different fabrication conditions. If the matrices are aged in ambient air before filling with a metal the inner surface of the porous silicon template offers a native SiOx layer due to the oxidation of the hydrogen terminated surface of the pore‐walls. Using as‐etched samples for deposition of the metal into the pores leads to the formation of a more complex interface during the cathodic deposition procedure which is observed by FTIR‐spectroscopy. Knowledge about the composition and the formation of the interior surface of the porous silicon matrix as well as the interface between semiconductor and metal is necessary on the one hand for interpretation of the gained experimental results and on the other hand to figure out possible applications of the fabricated hybrid system. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Catalysts effects on the production of carbon nanotubes by an automatic arc discharge set up in solution
Authors: Jahanshahi Mohsen , Seresht Razieh Jabari , Hajizadeh Solmaz 
Published: June 2009

AbstractCarbon nanotubes (CNTs) represent an important group of nanomaterials with attractive geometrical, electrical and chemical properties and are synthesized using a variety of techniques. CNTs have been extensively studied in our previous works and in this study were fabricated by arc discharge full automatic set up in liquid which does not require vacuum equipment, heat exchange system, active or inert gases. This technique was full automatic which enabled the controlling of gap between the two electrodes. The effect of the kind of catalyst on quantity of synthesized CNTs was studied herein. Carbon nanotubes were fabricated between two graphite electrodes which were submerged in the LiCl 0.25N as a solution and with a voltage of 25v. For comparative studies, Ni, Mo, Fe and Ni‐Mo were exploited as metallic or bimetallic catalysts and the results were subsequently analyzed, compared and discussed. In order to analyze the morphology of the synthesized products a scanning electron microscopy (SEM) as well as transmission electron microscopy (TEM) study were employed. Based on Mo‐Ni as catalysts in carbon electrode, high‐crystalline and alonged multi walled carbon nanotubes (MWCNTs), single walled carbon nanotubes (SWCNTs) and spring‐like carbon nanotubes (SCNTs) were synthesized by using this unique technique. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of stream flow patterns on riparian vegetation of a semiarid river: Implications for a changing climate
Authors: Stromberg J. C. , Lite S. J. , Dixon M. D. 
Published: June 2009

AbstractAs global climate change affects recharge and runoff processes, stream flow regimes are being altered. In the American Southwest, increasing aridity is predicted to cause declines in stream base flows and water tables. Another potential outcome of climate change is increased flood intensity. Changes in these stream flow conditions may independently affect vegetation or may have synergistic effects. Our goal was to extrapolate vegetation response to climate‐linked stream flow changes, by taking advantage of the spatial variation in flow conditions over a 200 km length of the San Pedro River (Arizona). Riparian vegetation traits were contrasted between sites differing in low‐flow hydrology (degree of stream intermittency) and flood intensity (stream power of the 10‐year recurrence flood). Field data indicate that increased stream intermittency would cause the floodplain plant community to shift from hydric pioneer trees and shrubs (Populus, Salix, Baccharis) towards mesic species (Tamarix). This shift in functional type would produce changes in vegetation structure, with reduced canopy cover and shorter canopies at drier sites. Among herbaceous species, annuals would increase while perennials would decrease. If flood intensities increased, there would be shifts towards younger tree age, expansion of xeric pioneer shrubs (in response to flood‐linked edaphic changes), and replacement of herbaceous perennials by annuals. Woody stem density would increase and basal area would decrease, reflecting shifts towards younger forests. Some effects would be compounded: Annuals were most prevalent, and tree canopies shortest, at sites that were dry and intensely flooded. Vegetational changes would feedback onto hydrologic and geomorphic processes, of importance for modeling. Increased flood intensity would have positive feedback on disturbance processes, by shifting plant communities towards species with less ability to stabilize sediments. Feedbacks between riparian vegetation and stream low‐flow changes would be homeostatic, with reduced evapotranspiration rates ameliorating declines in base flows arising from increased aridity. Copyright © 2009 John Wiley & Sons, Ltd.
Linking the hydraulic world of individual organisms to ecological processes: Putting ecology into ecohydraulics
Authors: Lancaster Jill , Downes Barbara J. 
Published: June 2009

AbstractEcohydraulics is a relatively new name for a long‐standing field investigating the interactions between ecology and the physics of flowing water. In recent decades, a burgeoning literature has developed relating species' densities to environmental variables, particularly those associated with flow. These abundance–environment relations (AERs) are sometimes used in habitat‐based association models (HAMs) to predict changes to species' abundances, especially human‐caused changes to the environment. Unfortunately, some conclusions arising from AERs are based on untenable ecological assertions or faulty assumptions including: illogical inference of cause‐and‐effect, muddling of hypotheses such as ‘habitat preference’ with other causal mechanisms, outdated ideas about environmental tolerance and optimization. Furthermore, the effects of biological interactions in AERs are routinely ignored, when biological interactions form the core of most modern models in community ecology. HAMs underpinned by AERs are often used to predict changes in populations, but lack information on demographic rates (births, deaths, migration), which are essential for population‐level predictions. These weaknesses are discussed at length and, we suggest, must be acknowledged and surmounted if ecohydraulics is to advance our understanding of stream ecosystems and our capacity to manage streams. We give two examples of research at the ecological–physical interface that are grounded in ecological principles: (1) how flow influences feeding rates of filter‐feeding insects (Simuliidae and Hydropsychidae) and the consequences for larval growth rates, adult body size and fecundity, and (2) how the physical factors that determine the density of rocks emergent from the water's surface may affect population densities of insects where females lay their eggs on emergent rocks. Ecohydraulics is an interdisciplinary field that requires expertise in both ecology and hydraulics, and true interdisciplinary teams may have the best prospects of addressing the many unanswered and untackled questions. Copyright © 2009 John Wiley & Sons, Ltd.
Bendway weirs: Could they create habitat for the endangered Rio Grande silvery minnow
Authors: Kinzli Kristoph‐Dietrich , Myrick Christopher A 
Published: June 2009

AbstractRehabilitation of the Middle Rio Grande in central New Mexico has become necessary to mitigate the effects of over a century of water and land development. The primary driving force behind rehabilitation efforts is the federally endangered Rio Grande silvery minnow (Hybognathus amarus). Bendway weirs, erosion control and channel‐stabilization structures placed transverse to the channel flow, have been used to prevent river migration while enhancing aquatic habitat. Habitat improvement plans on the Middle Rio Grande include the installation of bendway weirs, but the potential benefits of these structures for Rio Grande silvery minnow are unknown. We conducted a theoretical study on the flow conditions created by bendway weirs to determine if it is possible to create physical habitat for Rio Grande silvery minnow while simultaneously protecting the riverbank. Our study suggested that bendway weir installation could lead to the reduction of downstream displacement of Rio Grande silvery minnow eggs, the creation of Rio Grande silvery minnow feeding and refugia habitat, and the creation of drought or low flow habitat through scour hole formation. We also noted that the weirs could also serve as potential habitat for predators, and suggest further studies to better quantify the possible role of bendway weir installation. Copyright © 2009 John Wiley & Sons, Ltd.
Use of an energy filter to improve the spatial resolution of electron backscatter diffraction
Authors: Bhattacharyya Abhishek , Eades John A. 
Published: June 2009

AbstractThe electron backscatter diffraction (EBSD) analytical technique is invaluable for determining the crystallography of bulk alloys, thin films, and nanoparticles. However, our physical understanding of EBSD pattern generation is incomplete, which hinders our ability to push the limits of EBSD analysis. Here, by using an energy filter with better than 10 eV resolution, an improvement in the spatial resolution of the EBSD pattern was experimentally demonstrated. A signal depth of less than 15 nm for an aluminum film was achieved by controlling the cutoff energy of the energy filter. Additionally, a two‐fold improvement in the spatial resolution across a grain boundary was observed using the energy filter. SCANNING 31: 114–121, 2009. © 2009 Wiley Periodicals, Inc.
Multivariate statistical analysis applied to an IL6 signal transduction model in hepatocytes
Authors: McArdle Alison , Kruger Uwe , Hahn Juergen 
Published: June 2009

AbstractThis paper introduces the application of linear multivariate statistical techniques, including partial least squares (PLS), canonical correlation analysis (CCA) and reduced rank regression (RRR), into the area of Systems Biology. This new approach aims to extract the important proteins embedded in complex signal transduction pathway models.The analysis is performed on a model of intracellular signalling along the janus‐associated kinases/signal transducers and transcription factors (JAK/STAT) and mitogen activated protein kinases (MAPK) signal transduction pathways in interleukin‐6 (IL6)
stimulated hepatocytes, which produce signal transducer and activator of transcription factor 3 (STAT3).A region of redundancy within the MAPK pathway that does not affect the STAT3 transcription was identified using CCA. This is the core finding of this analysis and cannot be obtained by inspecting the model by eye. In addition, RRR was found to isolate terms that do not significantly contribute to changes in protein concentrations, while the application of PLS does not provide such a detailed picture by virtue of its construction.This analysis has a similar objective to conventional model reduction techniques with the advantage of maintaining the meaning of the states prior to and after the reduction process. A significant model reduction is performed, with a marginal loss in accuracy, offering a more concise model while maintaining the main influencing factors on the STAT3 transcription.The findings offer a deeper understanding of the reaction terms involved, confirm the relevance of several proteins to the production of Acute Phase Proteins and complement existing findings regarding cross‐talk between the two signalling pathways. Copyright © 2009 John Wiley & Sons, Ltd.