bluuebunny/crossref_metadata_2025_split huggingface dataset:
Recent advances in permafrost modelling
Authors: Riseborough Daniel , Shiklomanov Nikolay , Etzelmüller Bernd , Gruber Stephan , Marchenko Sergei 
Published: May 2008

AbstractThis paper provides a review of permafrost modelling advances, primarily since the 2003 permafrost conference in Zürich, Switzerland, with an emphasis on spatial permafrost models, in both arctic and high mountain environments. Models are categorised according to temporal, thermal and spatial criteria, and their approach to defining the relationship between climate, site surface conditions and permafrost status. The most significant recent advances include the expanding application of permafrost thermal models within spatial models, application of transient numerical thermal models within spatial models and incorporation of permafrost directly within global circulation model (GCM) land surface schemes. Future challenges for permafrost modelling will include establishing the appropriate level of integration required for accurate simulation of permafrost‐climate interaction within GCMs, the integration of environmental change such as treeline migration into permafrost response to climate change projections, and parameterising the effects of sub‐grid scale variability in surface processes and properties on small‐scale (large area) spatial models. Copyright © 2008 John Wiley & Sons, Ltd.
Advances in geophysical methods for permafrost investigations
Authors: Kneisel Christof , Hauck Christian , Fortier Richard , Moorman Brian 
Published: May 2008

AbstractGeophysical techniques can be used to examine the spatial distribution of subsurface geophysical properties to delineate horizontally and vertically the active layer, permafrost and taliks. Spatial and temporal changes in subsurface geophysical properties due to permafrost cooling, warming, aggradation or degradation can also be assessed through geophysical monitoring. This paper reviews the geophysical methods most frequently applied in mountain and arctic/subarctic lowland permafrost investigations. Key results and recommendations based on the analysis of the applicability and reliability of different geophysical techniques for permafrost studies are summarised. Emphasis is put on the tomographic capabilities of geophysical methods. Recent advances in application and data interpretation are shown in relation to five case studies, and future perspectives are highlighted. Copyright © 2008 John Wiley & Sons, Ltd.
Lowland periglacial research: a review of published advances 2003–2007
Authors: Humlum Ole , Christiansen Hanne H. 
Published: May 2008

AbstractResearch on lowland periglacial landforms and processes is reviewed using papers published from 2003–2007, to identify current interests, trends and directions of advances in knowledge, and to help identify promising avenues for future research. For this period, the total number of identified published research papers was 72. Topics relating to ice wedges, thermokarst, palsas and patterned ground were characterised by high publication activity. Current trends suggest three main research thrusts in the near‐future: palaeoenvironmental reconstructions (including Mars) using current process and landform observations as analogues, year‐round monitoring of processes using automatic equipment and modelling based on Geographical Information Systems. Copyright © 2008 John Wiley & Sons, Ltd.
Real‐time ultrasound measurements of changes in suboccipital vertebral artery diameter and blood flow velocity associated with cervical spine rotation
Authors: Mitchell Jeanette , Kramschuster Kristin 
Published: May 2008

AbstractBackground and Purpose. The vulnerability of the vertebral artery (VA) to distortion with sustained, full‐range cervical spine rotation, resulting in compromised blood flow and possible vertebrobasilar ischaemia, is well recognized. However, few studies have measured such blood flow changes in the parts of the VA downstream from the region of maximum cervical spine rotation: the suboccipital (VA3) and intracranial vertebral arteries. The purpose of this experimental study was to visualize the VA3 and record the changes in its blood flow associated with cervical spine rotation. Method. VA3 diameters and blood flow velocities were measured in the neutral cervical spine position and with active full‐range rotation to the left and right, in 35 healthy female subjects, using colour‐coded real‐time ultrasound. Results. Both left and right VA3 diameters and blood flow velocities decreased significantly on ipsilateral rotation. These values increased non‐significantly in the left VA3 and decreased non‐significantly in the right VA3 on contralateral rotation. Conclusions. The results of this study suggest that the distortion or compression of VA3 demonstrated by the reduction in diameter on ipsilateral cervical spine rotation, particularly, was sufficient to result in compromised blood flow. A significant stretching effect of VA3, on contralateral rotation, was not demonstrated in these subjects. Nevertheless, these findings add evidence to support the recommendation that sustained, full‐range cervical spine rotation should be avoided in professional practice. Copyright © 2008 John Wiley & Sons, Ltd.
Physical findings in patients with dizziness undergoing a group exercise programme
Authors: Kvåle Alice , Wilhelmsen Kjersti , Fiske Heidi Ann 
Published: May 2008

AbstractBackground and Purpose. Although there have been studies on patients with persistent dizziness, physical findings have not been formerly focused. The aim of this study was to investigate localization and extent of physical dysfunctions in patients with long‐lasting dizziness. To investigate physical change, we re‐examined patients who had completed a vestibular rehabilitation (VR) programme. Methods. A longitudinal design was used. Patients with peripheral vestibular dysfunction were examined with the Global Physiotherapy Examination (GPE‐52) and the Vertigo Symptom Scale‐short form (VSS‐SF). The GPE‐52 consists of 52 standardized items within posture, respiration, movement, muscle and skin. Initially, 32 patients were included; 20 completed the VR programme. The programme, based upon traditional VR exercises combined with a body awareness approach, was administered as group sessions taking place once weekly for nine weeks. Results. The majority of patients had a flexed head posture, and their respiration was restricted. Reduced flexibility, reduced ability to relax, measured with passive movements, and restricted range of motion (ROM) were found in about half of the patients in the neck, jaw, shoulder girdle and thorax. On palpation of muscles, 70–94% of the patients had reduced stretch in the abdominals/diaphragm, upper trapezius, sternocleidomastoid and medial gastrocnemius muscles. After the VR programme, significant improvements (p < 0.05) were shown in the following areas: respiration, flexibility and passive movement tests in the shoulder and cervical region, and ROM in the neck and jaw. Significant improvement (p < 0.05) was also reported in the balance subscale of the VSS‐SF. Conclusions. This study documents that postural changes, restricted respiration, lack of flexibility, ability to relax and reduced muscular stretch seem quite common in patients with dizziness. A modified VR comprising body awareness significantly improved respiration and movements in the upper body as well as self‐reported balance. Copyright © 2008 John Wiley & Sons, Ltd.
Crystal orientations of InSb films grown on a Si(111) substrate by inserting AlSb buffer layer
Authors: Murata K. , Ahmad N. B. , Mori M. , Tambo T. , Maezawa K. 
Published: May 2008

AbstractThe heteroepitaxial growth of InSb film via AlSb buffer layer on a Si(111) substrate was performed in an ultra high vacuum. The grown InSb films were characterized by X‐ray diffraction and atomic force microscopy. XRD patterns (ϕ‐scan) of the samples showed different epitaxial relationship between InSb/Si and InSb/AlSb/Si. It is found that surface condition has a significant influence on the growth of InSb films and the surface of InSb films became rough due to the high mixture ratio of domains. The two‐step growth procedure was also tried to further improve the crystal quality of the InSb films. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Studies on dynamics of charge carrier in organic electroluminescent devices
Authors: Takada N. , Kamata T. 
Published: May 2008

AbstractUnder high current density, lots of organic electroluminescent devices (OELDs) exhibit a substantial decrease in an external quantum coefficient (ηext). Understanding the operating principles of the device is necessary to control the ηext roll off and achieve good performance of OELDs. In this study, we mainly discuss the possible dynamics of charge carrier in our device according to the transient behaviors of electroluminescence (EL) and current after voltage pulse was turn off. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Theoretical design of carrier injection rate and recombination rate in tunnel injection quantum well lasers
Authors: Higa Yasutaka , Miyamoto Tomoyuki , Nakajima Hiroshi , Fujimoto Kosuke , Koyama Fumio 
Published: May 2008

AbstractCarrier injection rate in tunnel injection quantum well structures used in semiconductor lasers was investigated through theoretical analysis. Carrier capture time from 3D‐state to 2D‐state in a conventional quantum well was several ten picoseconds and it is almost uncontrollable characteristics. The tunnel injection structure can be designed to control the carrier injection rate. The carrier transition time from carrier reservoir‐region of the tunnel injection structure to the active well was a few picoseconds when the structure was designed for high speed transition. As results, carrier injection to ground state of the active well takes less than 10 picoseconds. The change of the radiative recombination rate in the active well also defines the optimal design of the tunnel injection structure. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of Si doping on size of GaN quantum dots grown by molecular beam epitaxy under Ga‐rich conditions
Authors: Managaki Nobuto , Iizuka Norio 
Published: May 2008

AbstractThe size control of Si‐doped GaN/AlN quantum dots (QDs) was studied by using molecular beam epitaxy under Ga‐rich conditions that were widely used for high‐quality thin‐film growth. The formation of GaN QDs was affected by Si‐doping in contrast with that of the QDs under N‐rich condition. Atomic force microscopy images of Si‐doped GaN QDs and undoped GaN QDs were clearly different. Diameters of Si‐doped GaN QDs decreased with increase in Si concentration within 1 x 1017‐1020 cm–3, whereas heights were almost constant. Micro‐Raman spectroscopy showed that the LO phonon frequency shifted toward lower wavenumbers with increase in Si concentration. These results suggest that Si doping may affect the length of Ga‐N bonds related with the elastic strain and, as a result, influence the aspect ratio of QDs. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Possible anomalous Hall effect of Be/Si pair delta‐doped GaAs structures
Authors: Noh J. P. , Jung D. W. , Islam A. Z. M. Touhidul , Otsuka N. 
Published: May 2008

AbstractBeryllium/Silicon pair delta‐doped GaAs structures grown by molecular‐beam epitaxy exhibit Hall resistance which has highly nonlinear dependence on the applied magnetic field. The dependence of the occurrence of the nonlinear Hall resistance on the sample structure is investigated. A significantly large increase in the non‐linearity and magnitude of the Hall resistance is observed from a sample structure whose buffer layer is grown under the low As flux and thick buffer layer condition. The non‐linearity of the Hall resistance is found to depend on a single parameter B /T, where B and T are the magnetic field and temperature, respectively. From another sample structure in which an AlGaAs barrier with a single Be delta‐doped layer is placed near the Be/Si pair delta‐doped layer, a similar nonlinear Hall resistance is observed. On the basis of these results, it is suggested that the anomalous Hall effect results from interplay between itinerant holes in the valence band and localized spins in the delta‐doped layer in these structures. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Spectral width dependence of residual carrier effect on nonlinear optical response of weakly confined excitons
Authors: Kojima O. , Isu T. , Ishi‐Hayase J. , Sasaki M. , Kanno A. , Katouf R. , Tsuchiya M. 
Published: May 2008

AbstractWe report residual carrier effects on the nonlinear optical response of weakly confined excitons in GaAs thin films. The nonlinear response was investigated using a degenerate four‐wave mixing technique with an additional pulse to create the residual carriers. In the case of the additional‐pulse incidence, the signal intensity decreases with the time of incidence.However, the ultrafast component comparable to the pulse width in the temporal profiles does not change appreciably. Our results imply the possibility of the realization of ultrafast switching using the exciton response. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
ZnO nanowires: chemical growth, electrodeposition, and application to intracellular nano‐sensors
Authors: Willander M. , Klason P. , Yang L. L. , Al‐Hilli Safaa M. , Zhao Q. X. , Nur O. 
Published: May 2008

AbstractIn this paper we present our results on growth, characterization, and nano‐devices based on ZnO nano‐structures. The ZnO nano‐structures were grown by mainly two methods, the catalytic Vapor Liquid Solid (VLS) and the low temperature chemical growth. We show that by multiple coating combined with low temperature chemical growth, well aligned with size controlled ZnO nanowires on silicon substrates can be achieved. The dissolution, due to its important on the stability of ZnO nano‐structures in aqueous medium, is then discussed and some preliminary experimental results are shown. Basic Optical characteristics of ZnO nano‐rods are briefly discussed. Finally, electrochemical intracellular nano‐sensors based on ZnO nano‐wires are demonstrated as efficient nano‐sensors for monitoring the human cell activity with minute pH changes. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Study of composition control and capping of MOVPE grown InGaN/InxAlyGa1–x–yN MQW structures
Authors: Ali M. , Suihkonen S. , Svensk O. , Törmä P. T. , Sopanen M. , Lipsanen H. , Odnoblyudov M. A. , Bougrov V. E. 
Published: May 2008

AbstractWe report on the growth and characterization of InGaN/ InxAlyGa1–x–yN multiple quantum well (MQW) structures emitting at 380 nm. The samples were grown by metalorganic vapour phase epitaxy (MOVPE) and were analyzed by using high resolution X‐ray diffraction (HRXRD), room and low temperature photoluminescence (PL) measurements. The effect of changing the indium precursor flow during the barrier and capping layer growth on the structural and optical quality of multiple quantum wells (MQWs) is explored. The HRXRD results show that the MQWs grown under the set of mentioned conditions are of very good structural quality. The temperature dependent PL results from our samples show that increasing the In content in the barriers enhances to a certain limit the internal quantum efficiency of the MQW structures. We also report that changing the In content in the capping layer effects the peak emission energy and does not have any significant impact on the optical quality of the MQW structures. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth and density control of GaN nanodots and nanopillars
Authors: Takeda S. , Inoue Y. , Ishida A. , Mimura H. 
Published: May 2008

AbstractWe have fabricated hexagonal pillar like GaN nanostructures on Si (111) substrate. The GaN nanopillars were grown by two step processes, including droplet epitaxy to form GaN nanodots as buffer, and hot wall epitaxy to grow GaN nanopillars. We proposed the growth mechanism of the GaN nanodot by droplet epitaxy. Density of the GaN nanopillars was controlled by changing the density of GaN nanodots. When the nanopillar density was so high as to coalesce with each other, the luminescence efficiency reduced. The deterioration of luminescence is considered to be due to increase of dislocations arising at the nanopillars interface. To obtain the high luminescence efficiency, it is important to increase density of nanopillars with no coalescing. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Quantum well and cavity structures grown on (110)GaAs by MBE
Authors: Hey R. , Jahn U. , Wan Qian , Trampert A. 
Published: May 2008

AbstractThe structural perfection of (In,Ga)As‐ and GaAs quantum wells and distributed Bragg reflectors for cavity structures on (110)GaAs grown by molecular‐beam epitaxy is investigated. The relaxation mechanism of accumulated elastic strain is studied by transmission electron microscopy.Differences to structures with (001) orientation are addressed. The use of short‐period superlattices for Bragg mirrors stabilizes the structures grown on (110)GaAs against relaxation‐based defect formation as well as degradation of bare sidewalls when exposed to ambient air. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth of semi‐polar (11‐22)GaN on a (113)Si substrate by selective MOVPE
Authors: Tanikawa T. , Hikosaka T. , Honda Y. , Yamaguchi M. , Sawaki N. 
Published: May 2008

AbstractMOVPE growth of uniform (11‐22)GaN layer was attempted on a patterned (113)Si substrate. The growth of GaN was achieved on (1‐11) facets of the Si selectively. The optimum design of the patterned substrate and the growth conditions were studied to get the semi‐polar GaN layer with high optical and crystalline quality. The cathode‐luminescence spectra showed a sharp edge emission peak of which half width was as narrow as 10 meV. The X‐ray rocking curves showed that the (11‐22) diffraction was as narrow as 300 arcsec. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Longitudinal‐commensurable resistance oscillations in the ballistic transport of electrons on cylindrical surfaces
Authors: Friedland K.‐J. , Hey R. , Kostial H. , Riedel A. 
Published: May 2008

AbstractWe observe a new type of resistance oscillations in the ballistic transport of two‐dimensional electrons on cylindrical surfaces with a tangentially directed magnetic field. The longitudinal resistance oscillates with a periodicity proportional to the square root of the magnetic field √B, which indicates a commensurability of longitudinal distances with a length scale related to the gradient of the perpendicular to the surface component of magnetic field B⊥.We show, that the length of the stripe with energetically free electrons, forming the so called ‘snake’‐like trajectories around the position where B⊥ = 0 is the basic length scale for the √B oscillations. We speculate, that ‘zitterbewegung’ of the one‐dimensional ‘skin’‐channel due to switching of the spin‐orbit interaction around the B⊥ = 0 position may cause this new type of resistance oscillations. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Current‐controlled wavelength tunability of a quantum cascade laser
Authors: Kim Gyungock , Jang Ki Seok , Kim In Gyoo , Lee Ki Joong 
Published: May 2008

AbstractWe report quantum cascade lasers (QCLs) which exhibit multiple peak structures in the emission spectra as a function of injected current, and provide the availability of additional laser lines in the single QCL. The emission spectra of quantum cascade lasers measured with varying current show emission wavelength peaks, separated by 110 nm, indicating the possibility of broad tuning range. The optical output power.vs. injected current curves also exhibit two separate thresholds at low duty cycles, indicating two different lasing conditions originating from the different transition levels. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of Indian monsoon daily rainfall on subseasonal to multidecadal time‐scales using a hidden Markov model
Authors: Greene A. M. , Robertson A. W. , Kirshner S. 
Published: May 2008

AbstractA 70‐year record of daily monsoon‐season rainfall at a network of 13 stations in central western India is analyzed using a 4‐state homogeneous hidden Markov model. The diagnosed states are seen to play distinct roles in the seasonal march of the monsoon, can be associated with ‘active’ and ‘break’ monsoon phases and capture the northward propagation of convective disturbances associated with the intraseasonal oscillation. Interannual variations in station rainfall are found to be associated with the alternation, from year to year, in the frequency of occurrence of wet and dry states; this mode of variability is well correlated with both all‐India monsoon rainfall and an index characterizing the strength of the El Niño Southern Oscillation. Analysis of low‐passed time series suggests that variations in state frequency are responsible for the modulation of monsoon rainfall on multidecadal time‐scales as well. Copyright © 2008 Royal Meteorological Society
The life cycle of convective‐shower cells under post‐frontal conditions
Authors: Weusthoff Tanja , Hauf Thomas 
Published: May 2008

AbstractSeventeen days with post‐frontal shower precipitation are analysed by means of radar data obtained from the German Weather Service's C‐band radar network. The life cycle of clusters—defined here as contiguous rain areas including one or more radar‐reflectivity peaks (i.e. convection cells)—is investigated. To allow for the continuous tracking of clusters, sometimes over a time period of more than an hour, a new, specially adapted tracking algorithm has been developed. The life cycle of convective clusters comprises five different stages: genesis; growth (including merging); stagnation; decay (including splitting); and dissolving. The transition likelihoods from a cluster with n maxima to one with m maxima are determined (the case m > n corresponding to growth and m < n to decay). It is found that, predominantly, clusters grow or decay by one cell. Results relating to the temporal evolution of post‐frontal showers are presented, and a conceptual growth model is proposed. Although single cells are the most frequent cluster type, the spatial structure of the post‐frontal precipitation field is dominated by multi‐celled clusters. Their life cycle is essentially affected by cell merging and splitting. Although the transitions of all (about one million) identified clusters have been analysed and quantified, more research is necessary in order to understand the underlying principles of cluster growth. Copyright © 2008 Royal Meteorological Society
Observation of microcontaminants on pure chromium surface by AFM and their removal by UV light illumination
Authors: Wang Rongguang 
Published: May 2008

AbstractMicrocontaminants on a pure chromium surface were observed and confirmed by atomic force microscope (AFM). On the basis of surface observation, X‐ray photoelectron spectroscopy (XPS) analysis and wettability measurement, the removal of microcontaminants by ultraviolet (UV) light illumination was investigated. Particle‐ and film‐like microcontaminants on the specimen surface were observed. With an increase in air exposure time, particle‐like contaminants increased in size, and then film‐like contaminants almost covered the entire surface. Most organic substance in the contaminants was removed by UV light illumination in a sealed chamber, except water in the contaminants. The re‐adhesion of contaminants on the UV‐light‐illuminated surface seemed slower after compared to before UV light illumination. Copyright © 2008 John Wiley & Sons, Ltd.